mirror of
https://github.com/octoleo/syncthing.git
synced 2024-12-22 02:48:59 +00:00
b10d106a55
This replaces old style errors.Wrap with modern fmt.Errorf and removes the (direct) dependency on github.com/pkg/errors. A couple of cases are adjusted by hand as previously errors.Wrap(nil, ...) would return nil, which is not what fmt.Errorf does.
103 lines
3.1 KiB
Go
103 lines
3.1 KiB
Go
// 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/.
|
|
|
|
//go:build !android
|
|
// +build !android
|
|
|
|
package osutil
|
|
|
|
import (
|
|
"fmt"
|
|
"os"
|
|
"syscall"
|
|
)
|
|
|
|
const ioprioClassShift = 13
|
|
|
|
type ioprioClass int
|
|
|
|
const (
|
|
ioprioClassRT ioprioClass = iota + 1
|
|
ioprioClassBE
|
|
ioprioClassIdle
|
|
)
|
|
|
|
const (
|
|
ioprioWhoProcess = iota + 1
|
|
ioprioWhoPGRP
|
|
ioprioWhoUser
|
|
)
|
|
|
|
func ioprioSet(class ioprioClass, value int) error {
|
|
res, _, err := syscall.Syscall(syscall.SYS_IOPRIO_SET,
|
|
uintptr(ioprioWhoProcess), 0,
|
|
uintptr(class)<<ioprioClassShift|uintptr(value))
|
|
if res == 0 {
|
|
return nil
|
|
}
|
|
return err
|
|
}
|
|
|
|
// SetLowPriority lowers the process CPU scheduling priority, and possibly
|
|
// I/O priority depending on the platform and OS.
|
|
func SetLowPriority() error {
|
|
// Process zero is "self", niceness value 9 is something between 0
|
|
// (default) and 19 (worst priority). But then, this is Linux, so of
|
|
// course we get this to take care of as well:
|
|
//
|
|
// "C library/kernel differences
|
|
//
|
|
// Within the kernel, nice values are actually represented using the
|
|
// range 40..1 (since negative numbers are error codes) and these are
|
|
// the values employed by the setpriority() and getpriority() system
|
|
// calls. The glibc wrapper functions for these system calls handle the
|
|
// translations between the user-land and kernel representations of the
|
|
// nice value according to the formula unice = 20 - knice. (Thus, the
|
|
// kernel's 40..1 range corresponds to the range -20..19 as seen by user
|
|
// space.)"
|
|
|
|
const (
|
|
pidSelf = 0
|
|
wantNiceLevel = 20 - 9
|
|
)
|
|
|
|
// Remember Linux kernel nice levels are upside down.
|
|
if cur, err := syscall.Getpriority(syscall.PRIO_PROCESS, 0); err == nil && cur <= wantNiceLevel {
|
|
// We're done here.
|
|
return nil
|
|
}
|
|
|
|
// Move ourselves to a new process group so that we can use the process
|
|
// group variants of Setpriority etc to affect all of our threads in one
|
|
// go. If this fails, bail, so that we don't affect things we shouldn't.
|
|
// If we are already the leader of our own process group, do nothing.
|
|
//
|
|
// Oh and this is because Linux doesn't follow the POSIX threading model
|
|
// where setting the niceness of the process would actually set the
|
|
// niceness of the process, instead it just affects the current thread
|
|
// so we need this workaround...
|
|
if pgid, err := syscall.Getpgid(pidSelf); err != nil {
|
|
// This error really shouldn't happen
|
|
return fmt.Errorf("get process group: %w", err)
|
|
} else if pgid != os.Getpid() {
|
|
// We are not process group leader. Elevate!
|
|
if err := syscall.Setpgid(pidSelf, 0); err != nil {
|
|
return fmt.Errorf("set process group: %w", err)
|
|
}
|
|
}
|
|
|
|
if err := syscall.Setpriority(syscall.PRIO_PGRP, pidSelf, wantNiceLevel); err != nil {
|
|
return fmt.Errorf("set niceness: %w", err)
|
|
}
|
|
|
|
// Best effort, somewhere to the end of the scale (0 through 7 being the
|
|
// range).
|
|
if err := ioprioSet(ioprioClassBE, 5); err != nil {
|
|
return fmt.Errorf("set I/O priority: %w", err)
|
|
}
|
|
return nil
|
|
}
|