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- // Copyright (C) 2018 The Syncthing Authors.
- //
- // This Source Code Form is subject to the terms of the Mozilla Public
- // License, v. 2.0. If a copy of the MPL was not distributed with this file,
- // You can obtain one at https://mozilla.org/MPL/2.0/.
- package osutil
- import (
- "syscall"
- "github.com/pkg/errors"
- )
- const (
- // https://msdn.microsoft.com/en-us/library/windows/desktop/ms686219(v=vs.85).aspx
- aboveNormalPriorityClass = 0x00008000
- belowNormalPriorityClass = 0x00004000
- highPriorityClass = 0x00000080
- idlePriorityClass = 0x00000040
- normalPriorityClass = 0x00000020
- processModeBackgroundBegin = 0x00100000
- processModeBackgroundEnd = 0x00200000
- realtimePriorityClass = 0x00000100
- )
- // SetLowPriority lowers the process CPU scheduling priority, and possibly
- // I/O priority depending on the platform and OS.
- func SetLowPriority() error {
- modkernel32 := syscall.NewLazyDLL("kernel32.dll")
- setPriorityClass := modkernel32.NewProc("SetPriorityClass")
- if err := setPriorityClass.Find(); err != nil {
- return errors.Wrap(err, "find proc")
- }
- handle, err := syscall.GetCurrentProcess()
- if err != nil {
- return errors.Wrap(err, "get process handler")
- }
- defer syscall.CloseHandle(handle)
- res, _, err := setPriorityClass.Call(uintptr(handle), belowNormalPriorityClass)
- if res != 0 {
- // "If the function succeeds, the return value is nonzero."
- return nil
- }
- return errors.Wrap(err, "set priority class") // wraps nil as nil
- }
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