dragora/patches/glib2/0001-gslice-remove-slice-allocator.patch

From a56821893c2f23eed656c94086ba7814c4a73e31 Mon Sep 17 00:00:00 2001
From: Natanael Copa <ncopa@alpinelinux.org>
Date: Wed, 5 Oct 2022 13:05:58 +0200
Subject: [PATCH] gslice: remove slice allocator

Keep the API for ABI compatibility.
fixes https://gitlab.gnome.org/GNOME/glib/-/issues/1079
---
 glib/gslice.c | 1560 +------------------------------------------------
 1 file changed, 20 insertions(+), 1540 deletions(-)

diff --git a/glib/gslice.c b/glib/gslice.c
index 36fa0841f..bf4f099b3 100644
--- a/glib/gslice.c
+++ b/glib/gslice.c
@@ -21,320 +21,23 @@
 #include "config.h"
 #include "glibconfig.h"
 
-#if defined(HAVE_POSIX_MEMALIGN) && !defined(_XOPEN_SOURCE)
-#define _XOPEN_SOURCE 600       /* posix_memalign() */
-#endif
-#include <stdlib.h>             /* posix_memalign() */
 #include <string.h>
-#include <errno.h>
-
-#ifdef G_OS_UNIX
-#include <unistd.h>             /* sysconf() */
-#endif
-#ifdef G_OS_WIN32
-#include <windows.h>
-#include <process.h>
-#endif
-
-#include <stdio.h>              /* fputs */
 
 #include "gslice.h"
 
-#include "gmain.h"
 #include "gmem.h"               /* gslice.h */
-#include "gstrfuncs.h"
-#include "gutils.h"
-#include "gtrashstack.h"
-#include "gtestutils.h"
-#include "gthread.h"
-#include "gthreadprivate.h"
 #include "glib_trace.h"
-#include "gprintf.h"
-
-#include "gvalgrind.h"
-
-/**
- * SECTION:memory_slices
- * @title: Memory Slices
- * @short_description: efficient way to allocate groups of equal-sized
- *     chunks of memory
- *
- * Memory slices provide a space-efficient and multi-processing scalable
- * way to allocate equal-sized pieces of memory, just like the original
- * #GMemChunks (from GLib 2.8), while avoiding their excessive
- * memory-waste, scalability and performance problems.
- *
- * To achieve these goals, the slice allocator uses a sophisticated,
- * layered design that has been inspired by Bonwick's slab allocator
- * ([Bonwick94](http://citeseer.ist.psu.edu/bonwick94slab.html)
- * Jeff Bonwick, The slab allocator: An object-caching kernel
- * memory allocator. USENIX 1994, and
- * [Bonwick01](http://citeseer.ist.psu.edu/bonwick01magazines.html)
- * Bonwick and Jonathan Adams, Magazines and vmem: Extending the
- * slab allocator to many cpu's and arbitrary resources. USENIX 2001)
- *
- * It uses posix_memalign() to optimize allocations of many equally-sized
- * chunks, and has per-thread free lists (the so-called magazine layer)
- * to quickly satisfy allocation requests of already known structure sizes.
- * This is accompanied by extra caching logic to keep freed memory around
- * for some time before returning it to the system. Memory that is unused
- * due to alignment constraints is used for cache colorization (random
- * distribution of chunk addresses) to improve CPU cache utilization. The
- * caching layer of the slice allocator adapts itself to high lock contention
- * to improve scalability.
- *
- * The slice allocator can allocate blocks as small as two pointers, and
- * unlike malloc(), it does not reserve extra space per block. For large block
- * sizes, g_slice_new() and g_slice_alloc() will automatically delegate to the
- * system malloc() implementation. For newly written code it is recommended
- * to use the new `g_slice` API instead of g_malloc() and
- * friends, as long as objects are not resized during their lifetime and the
- * object size used at allocation time is still available when freeing.
- *
- * Here is an example for using the slice allocator:
- * |[<!-- language="C" --> 
- * gchar *mem[10000];
- * gint i;
- *
- * // Allocate 10000 blocks.
- * for (i = 0; i < 10000; i++)
- *   {
- *     mem[i] = g_slice_alloc (50);
- *
- *     // Fill in the memory with some junk.
- *     for (j = 0; j < 50; j++)
- *       mem[i][j] = i * j;
- *   }
- *
- * // Now free all of the blocks.
- * for (i = 0; i < 10000; i++)
- *   g_slice_free1 (50, mem[i]);
- * ]|
- *
- * And here is an example for using the using the slice allocator
- * with data structures:
- * |[<!-- language="C" --> 
- * GRealArray *array;
- *
- * // Allocate one block, using the g_slice_new() macro.
- * array = g_slice_new (GRealArray);
- *
- * // We can now use array just like a normal pointer to a structure.
- * array->data            = NULL;
- * array->len             = 0;
- * array->alloc           = 0;
- * array->zero_terminated = (zero_terminated ? 1 : 0);
- * array->clear           = (clear ? 1 : 0);
- * array->elt_size        = elt_size;
- *
- * // We can free the block, so it can be reused.
- * g_slice_free (GRealArray, array);
- * ]|
- */
-
-/* the GSlice allocator is split up into 4 layers, roughly modelled after the slab
- * allocator and magazine extensions as outlined in:
- * + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel
- *   memory allocator. USENIX 1994, http://citeseer.ist.psu.edu/bonwick94slab.html
- * + [Bonwick01] Bonwick and Jonathan Adams, Magazines and vmem: Extending the
- *   slab allocator to many cpu's and arbitrary resources.
- *   USENIX 2001, http://citeseer.ist.psu.edu/bonwick01magazines.html
- * the layers are:
- * - the thread magazines. for each (aligned) chunk size, a magazine (a list)
- *   of recently freed and soon to be allocated chunks is maintained per thread.
- *   this way, most alloc/free requests can be quickly satisfied from per-thread
- *   free lists which only require one g_private_get() call to retrieve the
- *   thread handle.
- * - the magazine cache. allocating and freeing chunks to/from threads only
- *   occurs at magazine sizes from a global depot of magazines. the depot
- *   maintaines a 15 second working set of allocated magazines, so full
- *   magazines are not allocated and released too often.
- *   the chunk size dependent magazine sizes automatically adapt (within limits,
- *   see [3]) to lock contention to properly scale performance across a variety
- *   of SMP systems.
- * - the slab allocator. this allocator allocates slabs (blocks of memory) close
- *   to the system page size or multiples thereof which have to be page aligned.
- *   the blocks are divided into smaller chunks which are used to satisfy
- *   allocations from the upper layers. the space provided by the reminder of
- *   the chunk size division is used for cache colorization (random distribution
- *   of chunk addresses) to improve processor cache utilization. multiple slabs
- *   with the same chunk size are kept in a partially sorted ring to allow O(1)
- *   freeing and allocation of chunks (as long as the allocation of an entirely
- *   new slab can be avoided).
- * - the page allocator. on most modern systems, posix_memalign(3) or
- *   memalign(3) should be available, so this is used to allocate blocks with
- *   system page size based alignments and sizes or multiples thereof.
- *   if no memalign variant is provided, valloc() is used instead and
- *   block sizes are limited to the system page size (no multiples thereof).
- *   as a fallback, on system without even valloc(), a malloc(3)-based page
- *   allocator with alloc-only behaviour is used.
- *
- * NOTES:
- * [1] some systems memalign(3) implementations may rely on boundary tagging for
- *     the handed out memory chunks. to avoid excessive page-wise fragmentation,
- *     we reserve 2 * sizeof (void*) per block size for the systems memalign(3),
- *     specified in NATIVE_MALLOC_PADDING.
- * [2] using the slab allocator alone already provides for a fast and efficient
- *     allocator, it doesn't properly scale beyond single-threaded uses though.
- *     also, the slab allocator implements eager free(3)-ing, i.e. does not
- *     provide any form of caching or working set maintenance. so if used alone,
- *     it's vulnerable to trashing for sequences of balanced (alloc, free) pairs
- *     at certain thresholds.
- * [3] magazine sizes are bound by an implementation specific minimum size and
- *     a chunk size specific maximum to limit magazine storage sizes to roughly
- *     16KB.
- * [4] allocating ca. 8 chunks per block/page keeps a good balance between
- *     external and internal fragmentation (<= 12.5%). [Bonwick94]
- */
-
-/* --- macros and constants --- */
-#define LARGEALIGNMENT          (256)
-#define P2ALIGNMENT             (2 * sizeof (gsize))                            /* fits 2 pointers (assumed to be 2 * GLIB_SIZEOF_SIZE_T below) */
-#define ALIGN(size, base)       ((base) * (gsize) (((size) + (base) - 1) / (base)))
-#define NATIVE_MALLOC_PADDING   P2ALIGNMENT                                     /* per-page padding left for native malloc(3) see [1] */
-#define SLAB_INFO_SIZE          P2ALIGN (sizeof (SlabInfo) + NATIVE_MALLOC_PADDING)
-#define MAX_MAGAZINE_SIZE       (256)                                           /* see [3] and allocator_get_magazine_threshold() for this */
-#define MIN_MAGAZINE_SIZE       (4)
-#define MAX_STAMP_COUNTER       (7)                                             /* distributes the load of gettimeofday() */
-#define MAX_SLAB_CHUNK_SIZE(al) (((al)->max_page_size - SLAB_INFO_SIZE) / 8)    /* we want at last 8 chunks per page, see [4] */
-#define MAX_SLAB_INDEX(al)      (SLAB_INDEX (al, MAX_SLAB_CHUNK_SIZE (al)) + 1)
-#define SLAB_INDEX(al, asize)   ((asize) / P2ALIGNMENT - 1)                     /* asize must be P2ALIGNMENT aligned */
-#define SLAB_CHUNK_SIZE(al, ix) (((ix) + 1) * P2ALIGNMENT)
-#define SLAB_BPAGE_SIZE(al,csz) (8 * (csz) + SLAB_INFO_SIZE)
-
-/* optimized version of ALIGN (size, P2ALIGNMENT) */
-#if     GLIB_SIZEOF_SIZE_T * 2 == 8  /* P2ALIGNMENT */
-#define P2ALIGN(size)   (((size) + 0x7) & ~(gsize) 0x7)
-#elif   GLIB_SIZEOF_SIZE_T * 2 == 16 /* P2ALIGNMENT */
-#define P2ALIGN(size)   (((size) + 0xf) & ~(gsize) 0xf)
-#else
-#define P2ALIGN(size)   ALIGN (size, P2ALIGNMENT)
-#endif
-
-/* special helpers to avoid gmessage.c dependency */
-static void mem_error (const char *format, ...) G_GNUC_PRINTF (1,2);
-#define mem_assert(cond)    do { if (G_LIKELY (cond)) ; else mem_error ("assertion failed: %s", #cond); } while (0)
-
-/* --- structures --- */
-typedef struct _ChunkLink      ChunkLink;
-typedef struct _SlabInfo       SlabInfo;
-typedef struct _CachedMagazine CachedMagazine;
-struct _ChunkLink {
-  ChunkLink *next;
-  ChunkLink *data;
-};
-struct _SlabInfo {
-  ChunkLink *chunks;
-  guint n_allocated;
-  SlabInfo *next, *prev;
-};
-typedef struct {
-  ChunkLink *chunks;
-  gsize      count;                     /* approximative chunks list length */
-} Magazine;
-typedef struct {
-  Magazine   *magazine1;                /* array of MAX_SLAB_INDEX (allocator) */
-  Magazine   *magazine2;                /* array of MAX_SLAB_INDEX (allocator) */
-} ThreadMemory;
-typedef struct {
-  gboolean always_malloc;
-  gboolean bypass_magazines;
-  gboolean debug_blocks;
-  gsize    working_set_msecs;
-  guint    color_increment;
-} SliceConfig;
-typedef struct {
-  /* const after initialization */
-  gsize         min_page_size, max_page_size;
-  SliceConfig   config;
-  gsize         max_slab_chunk_size_for_magazine_cache;
-  /* magazine cache */
-  GMutex        magazine_mutex;
-  ChunkLink   **magazines;                /* array of MAX_SLAB_INDEX (allocator) */
-  guint        *contention_counters;      /* array of MAX_SLAB_INDEX (allocator) */
-  gint          mutex_counter;
-  guint         stamp_counter;
-  guint         last_stamp;
-  /* slab allocator */
-  GMutex        slab_mutex;
-  SlabInfo    **slab_stack;                /* array of MAX_SLAB_INDEX (allocator) */
-  guint        color_accu;
-} Allocator;
-
-/* --- g-slice prototypes --- */
-static gpointer     slab_allocator_alloc_chunk       (gsize      chunk_size);
-static void         slab_allocator_free_chunk        (gsize      chunk_size,
-                                                      gpointer   mem);
-static void         private_thread_memory_cleanup    (gpointer   data);
-static gpointer     allocator_memalign               (gsize      alignment,
-                                                      gsize      memsize);
-static void         allocator_memfree                (gsize      memsize,
-                                                      gpointer   mem);
-static inline void  magazine_cache_update_stamp      (void);
-static inline gsize allocator_get_magazine_threshold (Allocator *allocator,
-                                                      guint      ix);
-
-/* --- g-slice memory checker --- */
-static void     smc_notify_alloc  (void   *pointer,
-                                   size_t  size);
-static int      smc_notify_free   (void   *pointer,
-                                   size_t  size);
-
-/* --- variables --- */
-static GPrivate    private_thread_memory = G_PRIVATE_INIT (private_thread_memory_cleanup);
-static gsize       sys_page_size = 0;
-static Allocator   allocator[1] = { { 0, }, };
-static SliceConfig slice_config = {
-  FALSE,        /* always_malloc */
-  FALSE,        /* bypass_magazines */
-  FALSE,        /* debug_blocks */
-  15 * 1000,    /* working_set_msecs */
-  1,            /* color increment, alt: 0x7fffffff */
-};
-static GMutex      smc_tree_mutex; /* mutex for G_SLICE=debug-blocks */
 
 /* --- auxiliary functions --- */
 void
 g_slice_set_config (GSliceConfig ckey,
                     gint64       value)
-{
-  g_return_if_fail (sys_page_size == 0);
-  switch (ckey)
-    {
-    case G_SLICE_CONFIG_ALWAYS_MALLOC:
-      slice_config.always_malloc = value != 0;
-      break;
-    case G_SLICE_CONFIG_BYPASS_MAGAZINES:
-      slice_config.bypass_magazines = value != 0;
-      break;
-    case G_SLICE_CONFIG_WORKING_SET_MSECS:
-      slice_config.working_set_msecs = value;
-      break;
-    case G_SLICE_CONFIG_COLOR_INCREMENT:
-      slice_config.color_increment = value;
-      break;
-    default: ;
-    }
-}
+{ }
 
 gint64
 g_slice_get_config (GSliceConfig ckey)
 {
-  switch (ckey)
-    {
-    case G_SLICE_CONFIG_ALWAYS_MALLOC:
-      return slice_config.always_malloc;
-    case G_SLICE_CONFIG_BYPASS_MAGAZINES:
-      return slice_config.bypass_magazines;
-    case G_SLICE_CONFIG_WORKING_SET_MSECS:
-      return slice_config.working_set_msecs;
-    case G_SLICE_CONFIG_CHUNK_SIZES:
-      return MAX_SLAB_INDEX (allocator);
-    case G_SLICE_CONFIG_COLOR_INCREMENT:
-      return slice_config.color_increment;
-    default:
-      return 0;
-    }
+  return 0;
 }
 
 gint64*
@@ -342,566 +45,7 @@ g_slice_get_config_state (GSliceConfig ckey,
                           gint64       address,
                           guint       *n_values)
 {
-  guint i = 0;
-  g_return_val_if_fail (n_values != NULL, NULL);
-  *n_values = 0;
-  switch (ckey)
-    {
-      gint64 array[64];
-    case G_SLICE_CONFIG_CONTENTION_COUNTER:
-      array[i++] = SLAB_CHUNK_SIZE (allocator, address);
-      array[i++] = allocator->contention_counters[address];
-      array[i++] = allocator_get_magazine_threshold (allocator, address);
-      *n_values = i;
-      return g_memdup2 (array, sizeof (array[0]) * *n_values);
-    default:
-      return NULL;
-    }
-}
-
-static void
-slice_config_init (SliceConfig *config)
-{
-  const gchar *val;
-  gchar *val_allocated = NULL;
-
-  *config = slice_config;
-
-  /* Note that the empty string (`G_SLICE=""`) is treated differently from the
-   * envvar being unset. In the latter case, we also check whether running under
-   * valgrind. */
-#ifndef G_OS_WIN32
-  val = g_getenv ("G_SLICE");
-#else
-  /* The win32 implementation of g_getenv() has to do UTF-8 ↔ UTF-16 conversions
-   * which use the slice allocator, leading to deadlock. Use a simple in-place
-   * implementation here instead.
-   *
-   * Ignore references to other environment variables: only support values which
-   * are a combination of always-malloc and debug-blocks. */
-  {
-
-  wchar_t wvalue[128];  /* at least big enough for `always-malloc,debug-blocks` */
-  gsize len;
-
-  len = GetEnvironmentVariableW (L"G_SLICE", wvalue, G_N_ELEMENTS (wvalue));
-
-  if (len == 0)
-    {
-      if (GetLastError () == ERROR_ENVVAR_NOT_FOUND)
-        val = NULL;
-      else
-        val = "";
-    }
-  else if (len >= G_N_ELEMENTS (wvalue))
-    {
-      /* @wvalue isn’t big enough. Give up. */
-      g_warning ("Unsupported G_SLICE value");
-      val = NULL;
-    }
-  else
-    {
-      /* it’s safe to use g_utf16_to_utf8() here as it only allocates using
-       * malloc() rather than GSlice */
-      val = val_allocated = g_utf16_to_utf8 (wvalue, -1, NULL, NULL, NULL);
-    }
-
-  }
-#endif  /* G_OS_WIN32 */
-
-  if (val != NULL)
-    {
-      gint flags;
-      const GDebugKey keys[] = {
-        { "always-malloc", 1 << 0 },
-        { "debug-blocks",  1 << 1 },
-      };
-
-      flags = g_parse_debug_string (val, keys, G_N_ELEMENTS (keys));
-      if (flags & (1 << 0))
-        config->always_malloc = TRUE;
-      if (flags & (1 << 1))
-        config->debug_blocks = TRUE;
-    }
-  else
-    {
-      /* G_SLICE was not specified, so check if valgrind is running and
-       * disable ourselves if it is.
-       *
-       * This way it's possible to force gslice to be enabled under
-       * valgrind just by setting G_SLICE to the empty string.
-       */
-#ifdef ENABLE_VALGRIND
-      if (RUNNING_ON_VALGRIND)
-        config->always_malloc = TRUE;
-#endif
-    }
-
-  g_free (val_allocated);
-}
-
-static void
-g_slice_init_nomessage (void)
-{
-  /* we may not use g_error() or friends here */
-  mem_assert (sys_page_size == 0);
-  mem_assert (MIN_MAGAZINE_SIZE >= 4);
-
-#ifdef G_OS_WIN32
-  {
-    SYSTEM_INFO system_info;
-    GetSystemInfo (&system_info);
-    sys_page_size = system_info.dwPageSize;
-  }
-#else
-  sys_page_size = sysconf (_SC_PAGESIZE); /* = sysconf (_SC_PAGE_SIZE); = getpagesize(); */
-#endif
-  mem_assert (sys_page_size >= 2 * LARGEALIGNMENT);
-  mem_assert ((sys_page_size & (sys_page_size - 1)) == 0);
-  slice_config_init (&allocator->config);
-  allocator->min_page_size = sys_page_size;
-#if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN
-  /* allow allocation of pages up to 8KB (with 8KB alignment).
-   * this is useful because many medium to large sized structures
-   * fit less than 8 times (see [4]) into 4KB pages.
-   * we allow very small page sizes here, to reduce wastage in
-   * threads if only small allocations are required (this does
-   * bear the risk of increasing allocation times and fragmentation
-   * though).
-   */
-  allocator->min_page_size = MAX (allocator->min_page_size, 4096);
-  allocator->max_page_size = MAX (allocator->min_page_size, 8192);
-  allocator->min_page_size = MIN (allocator->min_page_size, 128);
-#else
-  /* we can only align to system page size */
-  allocator->max_page_size = sys_page_size;
-#endif
-  if (allocator->config.always_malloc)
-    {
-      allocator->contention_counters = NULL;
-      allocator->magazines = NULL;
-      allocator->slab_stack = NULL;
-    }
-  else
-    {
-      allocator->contention_counters = g_new0 (guint, MAX_SLAB_INDEX (allocator));
-      allocator->magazines = g_new0 (ChunkLink*, MAX_SLAB_INDEX (allocator));
-      allocator->slab_stack = g_new0 (SlabInfo*, MAX_SLAB_INDEX (allocator));
-    }
-
-  allocator->mutex_counter = 0;
-  allocator->stamp_counter = MAX_STAMP_COUNTER; /* force initial update */
-  allocator->last_stamp = 0;
-  allocator->color_accu = 0;
-  magazine_cache_update_stamp();
-  /* values cached for performance reasons */
-  allocator->max_slab_chunk_size_for_magazine_cache = MAX_SLAB_CHUNK_SIZE (allocator);
-  if (allocator->config.always_malloc || allocator->config.bypass_magazines)
-    allocator->max_slab_chunk_size_for_magazine_cache = 0;      /* non-optimized cases */
-}
-
-static inline guint
-allocator_categorize (gsize aligned_chunk_size)
-{
-  /* speed up the likely path */
-  if (G_LIKELY (aligned_chunk_size && aligned_chunk_size <= allocator->max_slab_chunk_size_for_magazine_cache))
-    return 1;           /* use magazine cache */
-
-  if (!allocator->config.always_malloc &&
-      aligned_chunk_size &&
-      aligned_chunk_size <= MAX_SLAB_CHUNK_SIZE (allocator))
-    {
-      if (allocator->config.bypass_magazines)
-        return 2;       /* use slab allocator, see [2] */
-      return 1;         /* use magazine cache */
-    }
-  return 0;             /* use malloc() */
-}
-
-static inline void
-g_mutex_lock_a (GMutex *mutex,
-                guint  *contention_counter)
-{
-  gboolean contention = FALSE;
-  if (!g_mutex_trylock (mutex))
-    {
-      g_mutex_lock (mutex);
-      contention = TRUE;
-    }
-  if (contention)
-    {
-      allocator->mutex_counter++;
-      if (allocator->mutex_counter >= 1)        /* quickly adapt to contention */
-        {
-          allocator->mutex_counter = 0;
-          *contention_counter = MIN (*contention_counter + 1, MAX_MAGAZINE_SIZE);
-        }
-    }
-  else /* !contention */
-    {
-      allocator->mutex_counter--;
-      if (allocator->mutex_counter < -11)       /* moderately recover magazine sizes */
-        {
-          allocator->mutex_counter = 0;
-          *contention_counter = MAX (*contention_counter, 1) - 1;
-        }
-    }
-}
-
-static inline ThreadMemory*
-thread_memory_from_self (void)
-{
-  ThreadMemory *tmem = g_private_get (&private_thread_memory);
-  if (G_UNLIKELY (!tmem))
-    {
-      static GMutex init_mutex;
-      guint n_magazines;
-
-      g_mutex_lock (&init_mutex);
-      if G_UNLIKELY (sys_page_size == 0)
-        g_slice_init_nomessage ();
-      g_mutex_unlock (&init_mutex);
-
-      n_magazines = MAX_SLAB_INDEX (allocator);
-      tmem = g_private_set_alloc0 (&private_thread_memory, sizeof (ThreadMemory) + sizeof (Magazine) * 2 * n_magazines);
-      tmem->magazine1 = (Magazine*) (tmem + 1);
-      tmem->magazine2 = &tmem->magazine1[n_magazines];
-    }
-  return tmem;
-}
-
-static inline ChunkLink*
-magazine_chain_pop_head (ChunkLink **magazine_chunks)
-{
-  /* magazine chains are linked via ChunkLink->next.
-   * each ChunkLink->data of the toplevel chain may point to a subchain,
-   * linked via ChunkLink->next. ChunkLink->data of the subchains just
-   * contains uninitialized junk.
-   */
-  ChunkLink *chunk = (*magazine_chunks)->data;
-  if (G_UNLIKELY (chunk))
-    {
-      /* allocating from freed list */
-      (*magazine_chunks)->data = chunk->next;
-    }
-  else
-    {
-      chunk = *magazine_chunks;
-      *magazine_chunks = chunk->next;
-    }
-  return chunk;
-}
-
-#if 0 /* useful for debugging */
-static guint
-magazine_count (ChunkLink *head)
-{
-  guint count = 0;
-  if (!head)
-    return 0;
-  while (head)
-    {
-      ChunkLink *child = head->data;
-      count += 1;
-      for (child = head->data; child; child = child->next)
-        count += 1;
-      head = head->next;
-    }
-  return count;
-}
-#endif
-
-static inline gsize
-allocator_get_magazine_threshold (Allocator *local_allocator,
-                                  guint ix)
-{
-  /* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE,
-   * which is required by the implementation. also, for moderately sized chunks
-   * (say >= 64 bytes), magazine sizes shouldn't be much smaller then the number
-   * of chunks available per page/2 to avoid excessive traffic in the magazine
-   * cache for small to medium sized structures.
-   * the upper bound of the magazine size is effectively provided by
-   * MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that
-   * the content of a single magazine doesn't exceed ca. 16KB.
-   */
-  gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
-  guint threshold = MAX (MIN_MAGAZINE_SIZE, local_allocator->max_page_size / MAX (5 * chunk_size, 5 * 32));
-  guint contention_counter = local_allocator->contention_counters[ix];
-  if (G_UNLIKELY (contention_counter))  /* single CPU bias */
-    {
-      /* adapt contention counter thresholds to chunk sizes */
-      contention_counter = contention_counter * 64 / chunk_size;
-      threshold = MAX (threshold, contention_counter);
-    }
-  return threshold;
-}
-
-/* --- magazine cache --- */
-static inline void
-magazine_cache_update_stamp (void)
-{
-  if (allocator->stamp_counter >= MAX_STAMP_COUNTER)
-    {
-      gint64 now_us = g_get_real_time ();
-      allocator->last_stamp = now_us / 1000; /* milli seconds */
-      allocator->stamp_counter = 0;
-    }
-  else
-    allocator->stamp_counter++;
-}
-
-static inline ChunkLink*
-magazine_chain_prepare_fields (ChunkLink *magazine_chunks)
-{
-  ChunkLink *chunk1;
-  ChunkLink *chunk2;
-  ChunkLink *chunk3;
-  ChunkLink *chunk4;
-  /* checked upon initialization: mem_assert (MIN_MAGAZINE_SIZE >= 4); */
-  /* ensure a magazine with at least 4 unused data pointers */
-  chunk1 = magazine_chain_pop_head (&magazine_chunks);
-  chunk2 = magazine_chain_pop_head (&magazine_chunks);
-  chunk3 = magazine_chain_pop_head (&magazine_chunks);
-  chunk4 = magazine_chain_pop_head (&magazine_chunks);
-  chunk4->next = magazine_chunks;
-  chunk3->next = chunk4;
-  chunk2->next = chunk3;
-  chunk1->next = chunk2;
-  return chunk1;
-}
-
-/* access the first 3 fields of a specially prepared magazine chain */
-#define magazine_chain_prev(mc)         ((mc)->data)
-#define magazine_chain_stamp(mc)        ((mc)->next->data)
-#define magazine_chain_uint_stamp(mc)   GPOINTER_TO_UINT ((mc)->next->data)
-#define magazine_chain_next(mc)         ((mc)->next->next->data)
-#define magazine_chain_count(mc)        ((mc)->next->next->next->data)
-
-static void
-magazine_cache_trim (Allocator *local_allocator,
-                     guint ix,
-                     guint stamp)
-{
-  /* g_mutex_lock (local_allocator->mutex); done by caller */
-  /* trim magazine cache from tail */
-  ChunkLink *current = magazine_chain_prev (local_allocator->magazines[ix]);
-  ChunkLink *trash = NULL;
-  while (!G_APPROX_VALUE (stamp, magazine_chain_uint_stamp (current),
-                          local_allocator->config.working_set_msecs))
-    {
-      /* unlink */
-      ChunkLink *prev = magazine_chain_prev (current);
-      ChunkLink *next = magazine_chain_next (current);
-      magazine_chain_next (prev) = next;
-      magazine_chain_prev (next) = prev;
-      /* clear special fields, put on trash stack */
-      magazine_chain_next (current) = NULL;
-      magazine_chain_count (current) = NULL;
-      magazine_chain_stamp (current) = NULL;
-      magazine_chain_prev (current) = trash;
-      trash = current;
-      /* fixup list head if required */
-      if (current == local_allocator->magazines[ix])
-        {
-          local_allocator->magazines[ix] = NULL;
-          break;
-        }
-      current = prev;
-    }
-  g_mutex_unlock (&local_allocator->magazine_mutex);
-  /* free trash */
-  if (trash)
-    {
-      const gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
-      g_mutex_lock (&local_allocator->slab_mutex);
-      while (trash)
-        {
-          current = trash;
-          trash = magazine_chain_prev (current);
-          magazine_chain_prev (current) = NULL; /* clear special field */
-          while (current)
-            {
-              ChunkLink *chunk = magazine_chain_pop_head (&current);
-              slab_allocator_free_chunk (chunk_size, chunk);
-            }
-        }
-      g_mutex_unlock (&local_allocator->slab_mutex);
-    }
-}
-
-static void
-magazine_cache_push_magazine (guint      ix,
-                              ChunkLink *magazine_chunks,
-                              gsize      count) /* must be >= MIN_MAGAZINE_SIZE */
-{
-  ChunkLink *current = magazine_chain_prepare_fields (magazine_chunks);
-  ChunkLink *next, *prev;
-  g_mutex_lock (&allocator->magazine_mutex);
-  /* add magazine at head */
-  next = allocator->magazines[ix];
-  if (next)
-    prev = magazine_chain_prev (next);
-  else
-    next = prev = current;
-  magazine_chain_next (prev) = current;
-  magazine_chain_prev (next) = current;
-  magazine_chain_prev (current) = prev;
-  magazine_chain_next (current) = next;
-  magazine_chain_count (current) = (gpointer) count;
-  /* stamp magazine */
-  magazine_cache_update_stamp();
-  magazine_chain_stamp (current) = GUINT_TO_POINTER (allocator->last_stamp);
-  allocator->magazines[ix] = current;
-  /* free old magazines beyond a certain threshold */
-  magazine_cache_trim (allocator, ix, allocator->last_stamp);
-  /* g_mutex_unlock (allocator->mutex); was done by magazine_cache_trim() */
-}
-
-static ChunkLink*
-magazine_cache_pop_magazine (guint  ix,
-                             gsize *countp)
-{
-  g_mutex_lock_a (&allocator->magazine_mutex, &allocator->contention_counters[ix]);
-  if (!allocator->magazines[ix])
-    {
-      guint magazine_threshold = allocator_get_magazine_threshold (allocator, ix);
-      gsize i, chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
-      ChunkLink *chunk, *head;
-      g_mutex_unlock (&allocator->magazine_mutex);
-      g_mutex_lock (&allocator->slab_mutex);
-      head = slab_allocator_alloc_chunk (chunk_size);
-      head->data = NULL;
-      chunk = head;
-      for (i = 1; i < magazine_threshold; i++)
-        {
-          chunk->next = slab_allocator_alloc_chunk (chunk_size);
-          chunk = chunk->next;
-          chunk->data = NULL;
-        }
-      chunk->next = NULL;
-      g_mutex_unlock (&allocator->slab_mutex);
-      *countp = i;
-      return head;
-    }
-  else
-    {
-      ChunkLink *current = allocator->magazines[ix];
-      ChunkLink *prev = magazine_chain_prev (current);
-      ChunkLink *next = magazine_chain_next (current);
-      /* unlink */
-      magazine_chain_next (prev) = next;
-      magazine_chain_prev (next) = prev;
-      allocator->magazines[ix] = next == current ? NULL : next;
-      g_mutex_unlock (&allocator->magazine_mutex);
-      /* clear special fields and hand out */
-      *countp = (gsize) magazine_chain_count (current);
-      magazine_chain_prev (current) = NULL;
-      magazine_chain_next (current) = NULL;
-      magazine_chain_count (current) = NULL;
-      magazine_chain_stamp (current) = NULL;
-      return current;
-    }
-}
-
-/* --- thread magazines --- */
-static void
-private_thread_memory_cleanup (gpointer data)
-{
-  ThreadMemory *tmem = data;
-  const guint n_magazines = MAX_SLAB_INDEX (allocator);
-  guint ix;
-  for (ix = 0; ix < n_magazines; ix++)
-    {
-      Magazine *mags[2];
-      guint j;
-      mags[0] = &tmem->magazine1[ix];
-      mags[1] = &tmem->magazine2[ix];
-      for (j = 0; j < 2; j++)
-        {
-          Magazine *mag = mags[j];
-          if (mag->count >= MIN_MAGAZINE_SIZE)
-            magazine_cache_push_magazine (ix, mag->chunks, mag->count);
-          else
-            {
-              const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
-              g_mutex_lock (&allocator->slab_mutex);
-              while (mag->chunks)
-                {
-                  ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
-                  slab_allocator_free_chunk (chunk_size, chunk);
-                }
-              g_mutex_unlock (&allocator->slab_mutex);
-            }
-        }
-    }
-  g_free (tmem);
-}
-
-static void
-thread_memory_magazine1_reload (ThreadMemory *tmem,
-                                guint         ix)
-{
-  Magazine *mag = &tmem->magazine1[ix];
-  mem_assert (mag->chunks == NULL); /* ensure that we may reset mag->count */
-  mag->count = 0;
-  mag->chunks = magazine_cache_pop_magazine (ix, &mag->count);
-}
-
-static void
-thread_memory_magazine2_unload (ThreadMemory *tmem,
-                                guint         ix)
-{
-  Magazine *mag = &tmem->magazine2[ix];
-  magazine_cache_push_magazine (ix, mag->chunks, mag->count);
-  mag->chunks = NULL;
-  mag->count = 0;
-}
-
-static inline void
-thread_memory_swap_magazines (ThreadMemory *tmem,
-                              guint         ix)
-{
-  Magazine xmag = tmem->magazine1[ix];
-  tmem->magazine1[ix] = tmem->magazine2[ix];
-  tmem->magazine2[ix] = xmag;
-}
-
-static inline gboolean
-thread_memory_magazine1_is_empty (ThreadMemory *tmem,
-                                  guint         ix)
-{
-  return tmem->magazine1[ix].chunks == NULL;
-}
-
-static inline gboolean
-thread_memory_magazine2_is_full (ThreadMemory *tmem,
-                                 guint         ix)
-{
-  return tmem->magazine2[ix].count >= allocator_get_magazine_threshold (allocator, ix);
-}
-
-static inline gpointer
-thread_memory_magazine1_alloc (ThreadMemory *tmem,
-                               guint         ix)
-{
-  Magazine *mag = &tmem->magazine1[ix];
-  ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
-  if (G_LIKELY (mag->count > 0))
-    mag->count--;
-  return chunk;
-}
-
-static inline void
-thread_memory_magazine2_free (ThreadMemory *tmem,
-                              guint         ix,
-                              gpointer      mem)
-{
-  Magazine *mag = &tmem->magazine2[ix];
-  ChunkLink *chunk = mem;
-  chunk->data = NULL;
-  chunk->next = mag->chunks;
-  mag->chunks = chunk;
-  mag->count++;
+  return NULL;
 }
 
 /* --- API functions --- */
@@ -915,9 +59,7 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  *
  * It calls g_slice_alloc() with `sizeof (@type)` and casts the
  * returned pointer to a pointer of the given type, avoiding a type
- * cast in the source code. Note that the underlying slice allocation
- * mechanism can be changed with the [`G_SLICE=always-malloc`][G_SLICE]
- * environment variable.
+ * cast in the source code.
  *
  * This can never return %NULL as the minimum allocation size from
  * `sizeof (@type)` is 1 byte.
@@ -938,9 +80,6 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  * It calls g_slice_alloc0() with `sizeof (@type)`
  * and casts the returned pointer to a pointer of the given type,
  * avoiding a type cast in the source code.
- * Note that the underlying slice allocation mechanism can
- * be changed with the [`G_SLICE=always-malloc`][G_SLICE]
- * environment variable.
  *
  * This can never return %NULL as the minimum allocation size from
  * `sizeof (@type)` is 1 byte.
@@ -962,9 +101,6 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  * It calls g_slice_copy() with `sizeof (@type)`
  * and casts the returned pointer to a pointer of the given type,
  * avoiding a type cast in the source code.
- * Note that the underlying slice allocation mechanism can
- * be changed with the [`G_SLICE=always-malloc`][G_SLICE]
- * environment variable.
  *
  * This can never return %NULL.
  *
@@ -985,8 +121,7 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  * It calls g_slice_free1() using `sizeof (type)`
  * as the block size.
  * Note that the exact release behaviour can be changed with the
- * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
- * [`G_SLICE`][G_SLICE] for related debugging options.
+ * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable.
  *
  * If @mem is %NULL, this macro does nothing.
  *
@@ -1006,8 +141,7 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  * a @next pointer (similar to #GSList). The name of the
  * @next field in @type is passed as third argument.
  * Note that the exact release behaviour can be changed with the
- * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
- * [`G_SLICE`][G_SLICE] for related debugging options.
+ * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable.
  *
  * If @mem_chain is %NULL, this function does nothing.
  *
@@ -1018,17 +152,7 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
  * g_slice_alloc:
  * @block_size: the number of bytes to allocate
  *
- * Allocates a block of memory from the slice allocator.
- *
- * The block address handed out can be expected to be aligned
- * to at least `1 * sizeof (void*)`, though in general slices
- * are `2 * sizeof (void*)` bytes aligned; if a `malloc()`
- * fallback implementation is used instead, the alignment may
- * be reduced in a libc dependent fashion.
- *
- * Note that the underlying slice allocation mechanism can
- * be changed with the [`G_SLICE=always-malloc`][G_SLICE]
- * environment variable.
+ * Allocates a block of memory from the libc allocator.
  *
  * Returns: a pointer to the allocated memory block, which will
  *   be %NULL if and only if @mem_size is 0
@@ -1038,43 +162,9 @@ thread_memory_magazine2_free (ThreadMemory *tmem,
 gpointer
 g_slice_alloc (gsize mem_size)
 {
-  ThreadMemory *tmem;
-  gsize chunk_size;
   gpointer mem;
-  guint acat;
-
-  /* This gets the private structure for this thread.  If the private
-   * structure does not yet exist, it is created.
-   *
-   * This has a side effect of causing GSlice to be initialised, so it
-   * must come first.
-   */
-  tmem = thread_memory_from_self ();
-
-  chunk_size = P2ALIGN (mem_size);
-  acat = allocator_categorize (chunk_size);
-  if (G_LIKELY (acat == 1))     /* allocate through magazine layer */
-    {
-      guint ix = SLAB_INDEX (allocator, chunk_size);
-      if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
-        {
-          thread_memory_swap_magazines (tmem, ix);
-          if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
-            thread_memory_magazine1_reload (tmem, ix);
-        }
-      mem = thread_memory_magazine1_alloc (tmem, ix);
-    }
-  else if (acat == 2)           /* allocate through slab allocator */
-    {
-      g_mutex_lock (&allocator->slab_mutex);
-      mem = slab_allocator_alloc_chunk (chunk_size);
-      g_mutex_unlock (&allocator->slab_mutex);
-    }
-  else                          /* delegate to system malloc */
-    mem = g_malloc (mem_size);
-  if (G_UNLIKELY (allocator->config.debug_blocks))
-    smc_notify_alloc (mem, mem_size);
 
+  mem = g_malloc (mem_size);
   TRACE (GLIB_SLICE_ALLOC((void*)mem, mem_size));
 
   return mem;
@@ -1085,9 +175,7 @@ g_slice_alloc (gsize mem_size)
  * @block_size: the number of bytes to allocate
  *
  * Allocates a block of memory via g_slice_alloc() and initializes
- * the returned memory to 0. Note that the underlying slice allocation
- * mechanism can be changed with the [`G_SLICE=always-malloc`][G_SLICE]
- * environment variable.
+ * the returned memory to 0.
  *
  * Returns: a pointer to the allocated block, which will be %NULL if and only
  *    if @mem_size is 0
@@ -1139,7 +227,7 @@ g_slice_copy (gsize         mem_size,
  * g_slice_alloc0() and the @block_size has to match the size
  * specified upon allocation. Note that the exact release behaviour
  * can be changed with the [`G_DEBUG=gc-friendly`][G_DEBUG] environment
- * variable, also see [`G_SLICE`][G_SLICE] for related debugging options.
+ * variable.
  *
  * If @mem_block is %NULL, this function does nothing.
  *
@@ -1149,41 +237,11 @@ void
 g_slice_free1 (gsize    mem_size,
                gpointer mem_block)
 {
-  gsize chunk_size = P2ALIGN (mem_size);
-  guint acat = allocator_categorize (chunk_size);
   if (G_UNLIKELY (!mem_block))
     return;
-  if (G_UNLIKELY (allocator->config.debug_blocks) &&
-      !smc_notify_free (mem_block, mem_size))
-    abort();
-  if (G_LIKELY (acat == 1))             /* allocate through magazine layer */
-    {
-      ThreadMemory *tmem = thread_memory_from_self();
-      guint ix = SLAB_INDEX (allocator, chunk_size);
-      if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
-        {
-          thread_memory_swap_magazines (tmem, ix);
-          if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
-            thread_memory_magazine2_unload (tmem, ix);
-        }
-      if (G_UNLIKELY (g_mem_gc_friendly))
-        memset (mem_block, 0, chunk_size);
-      thread_memory_magazine2_free (tmem, ix, mem_block);
-    }
-  else if (acat == 2)                   /* allocate through slab allocator */
-    {
-      if (G_UNLIKELY (g_mem_gc_friendly))
-        memset (mem_block, 0, chunk_size);
-      g_mutex_lock (&allocator->slab_mutex);
-      slab_allocator_free_chunk (chunk_size, mem_block);
-      g_mutex_unlock (&allocator->slab_mutex);
-    }
-  else                                  /* delegate to system malloc */
-    {
-      if (G_UNLIKELY (g_mem_gc_friendly))
-        memset (mem_block, 0, mem_size);
-      g_free (mem_block);
-    }
+  if (G_UNLIKELY (g_mem_gc_friendly))
+    memset (mem_block, 0, mem_size);
+  g_free (mem_block);
   TRACE (GLIB_SLICE_FREE((void*)mem_block, mem_size));
 }
 
@@ -1200,8 +258,7 @@ g_slice_free1 (gsize    mem_size,
  * @next pointer (similar to #GSList). The offset of the @next
  * field in each block is passed as third argument.
  * Note that the exact release behaviour can be changed with the
- * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
- * [`G_SLICE`][G_SLICE] for related debugging options.
+ * [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable.
  *
  * If @mem_chain is %NULL, this function does nothing.
  *
@@ -1213,589 +270,12 @@ g_slice_free_chain_with_offset (gsize    mem_size,
                                 gsize    next_offset)
 {
   gpointer slice = mem_chain;
-  /* while the thread magazines and the magazine cache are implemented so that
-   * they can easily be extended to allow for free lists containing more free
-   * lists for the first level nodes, which would allow O(1) freeing in this
-   * function, the benefit of such an extension is questionable, because:
-   * - the magazine size counts will become mere lower bounds which confuses
-   *   the code adapting to lock contention;
-   * - freeing a single node to the thread magazines is very fast, so this
-   *   O(list_length) operation is multiplied by a fairly small factor;
-   * - memory usage histograms on larger applications seem to indicate that
-   *   the amount of released multi node lists is negligible in comparison
-   *   to single node releases.
-   * - the major performance bottle neck, namely g_private_get() or
-   *   g_mutex_lock()/g_mutex_unlock() has already been moved out of the
-   *   inner loop for freeing chained slices.
-   */
-  gsize chunk_size = P2ALIGN (mem_size);
-  guint acat = allocator_categorize (chunk_size);
-  if (G_LIKELY (acat == 1))             /* allocate through magazine layer */
-    {
-      ThreadMemory *tmem = thread_memory_from_self();
-      guint ix = SLAB_INDEX (allocator, chunk_size);
-      while (slice)
-        {
-          guint8 *current = slice;
-          slice = *(gpointer*) (current + next_offset);
-          if (G_UNLIKELY (allocator->config.debug_blocks) &&
-              !smc_notify_free (current, mem_size))
-            abort();
-          if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
-            {
-              thread_memory_swap_magazines (tmem, ix);
-              if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
-                thread_memory_magazine2_unload (tmem, ix);
-            }
-          if (G_UNLIKELY (g_mem_gc_friendly))
-            memset (current, 0, chunk_size);
-          thread_memory_magazine2_free (tmem, ix, current);
-        }
-    }
-  else if (acat == 2)                   /* allocate through slab allocator */
-    {
-      g_mutex_lock (&allocator->slab_mutex);
-      while (slice)
-        {
-          guint8 *current = slice;
-          slice = *(gpointer*) (current + next_offset);
-          if (G_UNLIKELY (allocator->config.debug_blocks) &&
-              !smc_notify_free (current, mem_size))
-            abort();
-          if (G_UNLIKELY (g_mem_gc_friendly))
-            memset (current, 0, chunk_size);
-          slab_allocator_free_chunk (chunk_size, current);
-        }
-      g_mutex_unlock (&allocator->slab_mutex);
-    }
-  else                                  /* delegate to system malloc */
-    while (slice)
-      {
-        guint8 *current = slice;
-        slice = *(gpointer*) (current + next_offset);
-        if (G_UNLIKELY (allocator->config.debug_blocks) &&
-            !smc_notify_free (current, mem_size))
-          abort();
-        if (G_UNLIKELY (g_mem_gc_friendly))
-          memset (current, 0, mem_size);
-        g_free (current);
-      }
-}
-
-/* --- single page allocator --- */
-static void
-allocator_slab_stack_push (Allocator *local_allocator,
-                           guint ix,
-                           SlabInfo *sinfo)
-{
-  /* insert slab at slab ring head */
-  if (!local_allocator->slab_stack[ix])
-    {
-      sinfo->next = sinfo;
-      sinfo->prev = sinfo;
-    }
-  else
-    {
-      SlabInfo *next = local_allocator->slab_stack[ix], *prev = next->prev;
-      next->prev = sinfo;
-      prev->next = sinfo;
-      sinfo->next = next;
-      sinfo->prev = prev;
-    }
-  local_allocator->slab_stack[ix] = sinfo;
-}
-
-static gsize
-allocator_aligned_page_size (Allocator *local_allocator,
-                             gsize n_bytes)
-{
-  gsize val = (gsize) 1 << g_bit_storage (n_bytes - 1);
-  val = MAX (val, local_allocator->min_page_size);
-  return val;
-}
-
-static void
-allocator_add_slab (Allocator *local_allocator,
-                    guint ix,
-                    gsize chunk_size)
-{
-  ChunkLink *chunk;
-  SlabInfo *sinfo;
-  gsize addr, padding, n_chunks, color = 0;
-  gsize page_size;
-  int errsv;
-  gpointer aligned_memory;
-  guint8 *mem;
-  guint i;
-
-  page_size = allocator_aligned_page_size (local_allocator, SLAB_BPAGE_SIZE (local_allocator, chunk_size));
-  /* allocate 1 page for the chunks and the slab */
-  aligned_memory = allocator_memalign (page_size, page_size - NATIVE_MALLOC_PADDING);
-  errsv = errno;
-  mem = aligned_memory;
-
-  if (!mem)
-    {
-      const gchar *syserr = strerror (errsv);
-      mem_error ("failed to allocate %u bytes (alignment: %u): %s\n",
-                 (guint) (page_size - NATIVE_MALLOC_PADDING), (guint) page_size, syserr);
-    }
-  /* mask page address */
-  addr = ((gsize) mem / page_size) * page_size;
-  /* assert alignment */
-  mem_assert (aligned_memory == (gpointer) addr);
-  /* basic slab info setup */
-  sinfo = (SlabInfo*) (mem + page_size - SLAB_INFO_SIZE);
-  sinfo->n_allocated = 0;
-  sinfo->chunks = NULL;
-  /* figure cache colorization */
-  n_chunks = ((guint8*) sinfo - mem) / chunk_size;
-  padding = ((guint8*) sinfo - mem) - n_chunks * chunk_size;
-  if (padding)
-    {
-      color = (local_allocator->color_accu * P2ALIGNMENT) % padding;
-      local_allocator->color_accu += local_allocator->config.color_increment;
-    }
-  /* add chunks to free list */
-  chunk = (ChunkLink*) (mem + color);
-  sinfo->chunks = chunk;
-  for (i = 0; i < n_chunks - 1; i++)
-    {
-      chunk->next = (ChunkLink*) ((guint8*) chunk + chunk_size);
-      chunk = chunk->next;
-    }
-  chunk->next = NULL;   /* last chunk */
-  /* add slab to slab ring */
-  allocator_slab_stack_push (local_allocator, ix, sinfo);
-}
-
-static gpointer
-slab_allocator_alloc_chunk (gsize chunk_size)
-{
-  ChunkLink *chunk;
-  guint ix = SLAB_INDEX (allocator, chunk_size);
-  /* ensure non-empty slab */
-  if (!allocator->slab_stack[ix] || !allocator->slab_stack[ix]->chunks)
-    allocator_add_slab (allocator, ix, chunk_size);
-  /* allocate chunk */
-  chunk = allocator->slab_stack[ix]->chunks;
-  allocator->slab_stack[ix]->chunks = chunk->next;
-  allocator->slab_stack[ix]->n_allocated++;
-  /* rotate empty slabs */
-  if (!allocator->slab_stack[ix]->chunks)
-    allocator->slab_stack[ix] = allocator->slab_stack[ix]->next;
-  return chunk;
-}
-
-static void
-slab_allocator_free_chunk (gsize    chunk_size,
-                           gpointer mem)
-{
-  ChunkLink *chunk;
-  gboolean was_empty;
-  guint ix = SLAB_INDEX (allocator, chunk_size);
-  gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size));
-  gsize addr = ((gsize) mem / page_size) * page_size;
-  /* mask page address */
-  guint8 *page = (guint8*) addr;
-  SlabInfo *sinfo = (SlabInfo*) (page + page_size - SLAB_INFO_SIZE);
-  /* assert valid chunk count */
-  mem_assert (sinfo->n_allocated > 0);
-  /* add chunk to free list */
-  was_empty = sinfo->chunks == NULL;
-  chunk = (ChunkLink*) mem;
-  chunk->next = sinfo->chunks;
-  sinfo->chunks = chunk;
-  sinfo->n_allocated--;
-  /* keep slab ring partially sorted, empty slabs at end */
-  if (was_empty)
-    {
-      /* unlink slab */
-      SlabInfo *next = sinfo->next, *prev = sinfo->prev;
-      next->prev = prev;
-      prev->next = next;
-      if (allocator->slab_stack[ix] == sinfo)
-        allocator->slab_stack[ix] = next == sinfo ? NULL : next;
-      /* insert slab at head */
-      allocator_slab_stack_push (allocator, ix, sinfo);
-    }
-  /* eagerly free complete unused slabs */
-  if (!sinfo->n_allocated)
-    {
-      /* unlink slab */
-      SlabInfo *next = sinfo->next, *prev = sinfo->prev;
-      next->prev = prev;
-      prev->next = next;
-      if (allocator->slab_stack[ix] == sinfo)
-        allocator->slab_stack[ix] = next == sinfo ? NULL : next;
-      /* free slab */
-      allocator_memfree (page_size, page);
-    }
-}
-
-/* --- memalign implementation --- */
-#ifdef HAVE_MALLOC_H
-#include <malloc.h>             /* memalign() */
-#endif
-
-/* from config.h:
- * define HAVE_POSIX_MEMALIGN           1 // if free(posix_memalign(3)) works, <stdlib.h>
- * define HAVE_MEMALIGN                 1 // if free(memalign(3)) works, <malloc.h>
- * define HAVE_VALLOC                   1 // if free(valloc(3)) works, <stdlib.h> or <malloc.h>
- * if none is provided, we implement malloc(3)-based alloc-only page alignment
- */
-
-#if !(HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC)
-G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-static GTrashStack *compat_valloc_trash = NULL;
-G_GNUC_END_IGNORE_DEPRECATIONS
-#endif
-
-static gpointer
-allocator_memalign (gsize alignment,
-                    gsize memsize)
-{
-  gpointer aligned_memory = NULL;
-  gint err = ENOMEM;
-#if     HAVE_POSIX_MEMALIGN
-  err = posix_memalign (&aligned_memory, alignment, memsize);
-#elif   HAVE_MEMALIGN
-  errno = 0;
-  aligned_memory = memalign (alignment, memsize);
-  err = errno;
-#elif   HAVE_VALLOC
-  errno = 0;
-  aligned_memory = valloc (memsize);
-  err = errno;
-#else
-  /* simplistic non-freeing page allocator */
-  mem_assert (alignment == sys_page_size);
-  mem_assert (memsize <= sys_page_size);
-  if (!compat_valloc_trash)
-    {
-      const guint n_pages = 16;
-      guint8 *mem = malloc (n_pages * sys_page_size);
-      err = errno;
-      if (mem)
-        {
-          gint i = n_pages;
-          guint8 *amem = (guint8*) ALIGN ((gsize) mem, sys_page_size);
-          if (amem != mem)
-            i--;        /* mem wasn't page aligned */
-          G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-          while (--i >= 0)
-            g_trash_stack_push (&compat_valloc_trash, amem + i * sys_page_size);
-          G_GNUC_END_IGNORE_DEPRECATIONS
-        }
-    }
-  G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-  aligned_memory = g_trash_stack_pop (&compat_valloc_trash);
-  G_GNUC_END_IGNORE_DEPRECATIONS
-#endif
-  if (!aligned_memory)
-    errno = err;
-  return aligned_memory;
-}
-
-static void
-allocator_memfree (gsize    memsize,
-                   gpointer mem)
-{
-#if     HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC
-  free (mem);
-#else
-  mem_assert (memsize <= sys_page_size);
-  G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-  g_trash_stack_push (&compat_valloc_trash, mem);
-  G_GNUC_END_IGNORE_DEPRECATIONS
-#endif
-}
-
-static void
-mem_error (const char *format,
-           ...)
-{
-  const char *pname;
-  va_list args;
-  /* at least, put out "MEMORY-ERROR", in case we segfault during the rest of the function */
-  fputs ("\n***MEMORY-ERROR***: ", stderr);
-  pname = g_get_prgname();
-  g_fprintf (stderr, "%s[%ld]: GSlice: ", pname ? pname : "", (long)getpid());
-  va_start (args, format);
-  g_vfprintf (stderr, format, args);
-  va_end (args);
-  fputs ("\n", stderr);
-  abort();
-  _exit (1);
-}
-
-/* --- g-slice memory checker tree --- */
-typedef size_t SmcKType;                /* key type */
-typedef size_t SmcVType;                /* value type */
-typedef struct {
-  SmcKType key;
-  SmcVType value;
-} SmcEntry;
-static void             smc_tree_insert      (SmcKType  key,
-                                              SmcVType  value);
-static gboolean         smc_tree_lookup      (SmcKType  key,
-                                              SmcVType *value_p);
-static gboolean         smc_tree_remove      (SmcKType  key);
-
-
-/* --- g-slice memory checker implementation --- */
-static void
-smc_notify_alloc (void   *pointer,
-                  size_t  size)
-{
-  size_t address = (size_t) pointer;
-  if (pointer)
-    smc_tree_insert (address, size);
-}
-
-#if 0
-static void
-smc_notify_ignore (void *pointer)
-{
-  size_t address = (size_t) pointer;
-  if (pointer)
-    smc_tree_remove (address);
-}
-#endif
-
-static int
-smc_notify_free (void   *pointer,
-                 size_t  size)
-{
-  size_t address = (size_t) pointer;
-  SmcVType real_size;
-  gboolean found_one;
-
-  if (!pointer)
-    return 1; /* ignore */
-  found_one = smc_tree_lookup (address, &real_size);
-  if (!found_one)
-    {
-      g_fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
-      return 0;
-    }
-  if (real_size != size && (real_size || size))
-    {
-      g_fprintf (stderr, "GSlice: MemChecker: attempt to release block with invalid size: %p size=%" G_GSIZE_FORMAT " invalid-size=%" G_GSIZE_FORMAT "\n", pointer, real_size, size);
-      return 0;
-    }
-  if (!smc_tree_remove (address))
-    {
-      g_fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
-      return 0;
-    }
-  return 1; /* all fine */
-}
-
-/* --- g-slice memory checker tree implementation --- */
-#define SMC_TRUNK_COUNT     (4093 /* 16381 */)          /* prime, to distribute trunk collisions (big, allocated just once) */
-#define SMC_BRANCH_COUNT    (511)                       /* prime, to distribute branch collisions */
-#define SMC_TRUNK_EXTENT    (SMC_BRANCH_COUNT * 2039)   /* key address space per trunk, should distribute uniformly across BRANCH_COUNT */
-#define SMC_TRUNK_HASH(k)   ((k / SMC_TRUNK_EXTENT) % SMC_TRUNK_COUNT)  /* generate new trunk hash per megabyte (roughly) */
-#define SMC_BRANCH_HASH(k)  (k % SMC_BRANCH_COUNT)
-
-typedef struct {
-  SmcEntry    *entries;
-  unsigned int n_entries;
-} SmcBranch;
-
-static SmcBranch     **smc_tree_root = NULL;
-
-static void
-smc_tree_abort (int errval)
-{
-  const char *syserr = strerror (errval);
-  mem_error ("MemChecker: failure in debugging tree: %s", syserr);
-}
-
-static inline SmcEntry*
-smc_tree_branch_grow_L (SmcBranch   *branch,
-                        unsigned int index)
-{
-  unsigned int old_size = branch->n_entries * sizeof (branch->entries[0]);
-  unsigned int new_size = old_size + sizeof (branch->entries[0]);
-  SmcEntry *entry;
-  mem_assert (index <= branch->n_entries);
-  branch->entries = (SmcEntry*) realloc (branch->entries, new_size);
-  if (!branch->entries)
-    smc_tree_abort (errno);
-  entry = branch->entries + index;
-  memmove (entry + 1, entry, (branch->n_entries - index) * sizeof (entry[0]));
-  branch->n_entries += 1;
-  return entry;
-}
-
-static inline SmcEntry*
-smc_tree_branch_lookup_nearest_L (SmcBranch *branch,
-                                  SmcKType   key)
-{
-  unsigned int n_nodes = branch->n_entries, offs = 0;
-  SmcEntry *check = branch->entries;
-  int cmp = 0;
-  while (offs < n_nodes)
-    {
-      unsigned int i = (offs + n_nodes) >> 1;
-      check = branch->entries + i;
-      cmp = key < check->key ? -1 : key != check->key;
-      if (cmp == 0)
-        return check;                   /* return exact match */
-      else if (cmp < 0)
-        n_nodes = i;
-      else /* (cmp > 0) */
-        offs = i + 1;
-    }
-  /* check points at last mismatch, cmp > 0 indicates greater key */
-  return cmp > 0 ? check + 1 : check;   /* return insertion position for inexact match */
-}
-
-static void
-smc_tree_insert (SmcKType key,
-                 SmcVType value)
-{
-  unsigned int ix0, ix1;
-  SmcEntry *entry;
-
-  g_mutex_lock (&smc_tree_mutex);
-  ix0 = SMC_TRUNK_HASH (key);
-  ix1 = SMC_BRANCH_HASH (key);
-  if (!smc_tree_root)
-    {
-      smc_tree_root = calloc (SMC_TRUNK_COUNT, sizeof (smc_tree_root[0]));
-      if (!smc_tree_root)
-        smc_tree_abort (errno);
-    }
-  if (!smc_tree_root[ix0])
+  while (slice)
     {
-      smc_tree_root[ix0] = calloc (SMC_BRANCH_COUNT, sizeof (smc_tree_root[0][0]));
-      if (!smc_tree_root[ix0])
-        smc_tree_abort (errno);
-    }
-  entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
-  if (!entry ||                                                                         /* need create */
-      entry >= smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries ||   /* need append */
-      entry->key != key)                                                                /* need insert */
-    entry = smc_tree_branch_grow_L (&smc_tree_root[ix0][ix1], entry - smc_tree_root[ix0][ix1].entries);
-  entry->key = key;
-  entry->value = value;
-  g_mutex_unlock (&smc_tree_mutex);
-}
-
-static gboolean
-smc_tree_lookup (SmcKType  key,
-                 SmcVType *value_p)
-{
-  SmcEntry *entry = NULL;
-  unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
-  gboolean found_one = FALSE;
-  *value_p = 0;
-  g_mutex_lock (&smc_tree_mutex);
-  if (smc_tree_root && smc_tree_root[ix0])
-    {
-      entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
-      if (entry &&
-          entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
-          entry->key == key)
-        {
-          found_one = TRUE;
-          *value_p = entry->value;
-        }
-    }
-  g_mutex_unlock (&smc_tree_mutex);
-  return found_one;
-}
-
-static gboolean
-smc_tree_remove (SmcKType key)
-{
-  unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
-  gboolean found_one = FALSE;
-  g_mutex_lock (&smc_tree_mutex);
-  if (smc_tree_root && smc_tree_root[ix0])
-    {
-      SmcEntry *entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
-      if (entry &&
-          entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
-          entry->key == key)
-        {
-          unsigned int i = entry - smc_tree_root[ix0][ix1].entries;
-          smc_tree_root[ix0][ix1].n_entries -= 1;
-          memmove (entry, entry + 1, (smc_tree_root[ix0][ix1].n_entries - i) * sizeof (entry[0]));
-          if (!smc_tree_root[ix0][ix1].n_entries)
-            {
-              /* avoid useless pressure on the memory system */
-              free (smc_tree_root[ix0][ix1].entries);
-              smc_tree_root[ix0][ix1].entries = NULL;
-            }
-          found_one = TRUE;
-        }
-    }
-  g_mutex_unlock (&smc_tree_mutex);
-  return found_one;
-}
-
-#ifdef G_ENABLE_DEBUG
-void
-g_slice_debug_tree_statistics (void)
-{
-  g_mutex_lock (&smc_tree_mutex);
-  if (smc_tree_root)
-    {
-      unsigned int i, j, t = 0, o = 0, b = 0, su = 0, ex = 0, en = 4294967295u;
-      double tf, bf;
-      for (i = 0; i < SMC_TRUNK_COUNT; i++)
-        if (smc_tree_root[i])
-          {
-            t++;
-            for (j = 0; j < SMC_BRANCH_COUNT; j++)
-              if (smc_tree_root[i][j].n_entries)
-                {
-                  b++;
-                  su += smc_tree_root[i][j].n_entries;
-                  en = MIN (en, smc_tree_root[i][j].n_entries);
-                  ex = MAX (ex, smc_tree_root[i][j].n_entries);
-                }
-              else if (smc_tree_root[i][j].entries)
-                o++; /* formerly used, now empty */
-          }
-      en = b ? en : 0;
-      tf = MAX (t, 1.0); /* max(1) to be a valid divisor */
-      bf = MAX (b, 1.0); /* max(1) to be a valid divisor */
-      g_fprintf (stderr, "GSlice: MemChecker: %u trunks, %u branches, %u old branches\n", t, b, o);
-      g_fprintf (stderr, "GSlice: MemChecker: %f branches per trunk, %.2f%% utilization\n",
-               b / tf,
-               100.0 - (SMC_BRANCH_COUNT - b / tf) / (0.01 * SMC_BRANCH_COUNT));
-      g_fprintf (stderr, "GSlice: MemChecker: %f entries per branch, %u minimum, %u maximum\n",
-               su / bf, en, ex);
+      guint8 *current = slice;
+      slice = *(gpointer*) (current + next_offset);
+      if (G_UNLIKELY (g_mem_gc_friendly))
+        memset (current, 0, mem_size);
+      g_free (current);
     }
-  else
-    g_fprintf (stderr, "GSlice: MemChecker: root=NULL\n");
-  g_mutex_unlock (&smc_tree_mutex);
-  
-  /* sample statistics (beast + GSLice + 24h scripted core & GUI activity):
-   *  PID %CPU %MEM   VSZ  RSS      COMMAND
-   * 8887 30.3 45.8 456068 414856   beast-0.7.1 empty.bse
-   * $ cat /proc/8887/statm # total-program-size resident-set-size shared-pages text/code data/stack library dirty-pages
-   * 114017 103714 2354 344 0 108676 0
-   * $ cat /proc/8887/status 
-   * Name:   beast-0.7.1
-   * VmSize:   456068 kB
-   * VmLck:         0 kB
-   * VmRSS:    414856 kB
-   * VmData:   434620 kB
-   * VmStk:        84 kB
-   * VmExe:      1376 kB
-   * VmLib:     13036 kB
-   * VmPTE:       456 kB
-   * Threads:        3
-   * (gdb) print g_slice_debug_tree_statistics ()
-   * GSlice: MemChecker: 422 trunks, 213068 branches, 0 old branches
-   * GSlice: MemChecker: 504.900474 branches per trunk, 98.81% utilization
-   * GSlice: MemChecker: 4.965039 entries per branch, 1 minimum, 37 maximum
-   */
 }
-#endif /* G_ENABLE_DEBUG */
-- 
2.38.1