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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
* vi:set noexpandtab tabstop=8 shiftwidth=8:
*
* Copyright (C) 2005, Novell, Inc.
* Copyright (C) 2006, Jamie McCracken <jamiemcc@gnome.org>
* Copyright (C) 2006, Anders Aagaard
*
* Based mostly on code by Robert Love <rml@novell.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "config.h"
#ifdef __linux__
#include <stdio.h>
#include <errno.h>
#ifdef HAVE_LINUX_UNISTD_H
#include <linux/unistd.h>
#endif
#include <sys/syscall.h>
#include <unistd.h>
#include <glib/gstdio.h>
#endif /* __linux__ */
#include "gs-ioprio.h"
/* We assume ALL linux architectures have the syscalls defined here */
#ifdef __linux__
/* Make sure the system call is supported */
#ifndef __NR_ioprio_set
#if defined(__i386__)
#define __NR_ioprio_set 289
#define __NR_ioprio_get 290
#elif defined(__powerpc__) || defined(__powerpc64__)
#define __NR_ioprio_set 273
#define __NR_ioprio_get 274
#elif defined(__x86_64__)
#define __NR_ioprio_set 251
#define __NR_ioprio_get 252
#elif defined(__ia64__)
#define __NR_ioprio_set 1274
#define __NR_ioprio_get 1275
#elif defined(__alpha__)
#define __NR_ioprio_set 442
#define __NR_ioprio_get 443
#elif defined(__s390x__) || defined(__s390__)
#define __NR_ioprio_set 282
#define __NR_ioprio_get 283
#elif defined(__SH4__)
#define __NR_ioprio_set 288
#define __NR_ioprio_get 289
#elif defined(__SH5__)
#define __NR_ioprio_set 316
#define __NR_ioprio_get 317
#elif defined(__sparc__) || defined(__sparc64__)
#define __NR_ioprio_set 196
#define __NR_ioprio_get 218
#elif defined(__arm__)
#define __NR_ioprio_set 314
#define __NR_ioprio_get 315
#else
#error "Unsupported architecture!"
#endif
#endif /* __NR_ioprio_set */
enum {
IOPRIO_CLASS_NONE,
IOPRIO_CLASS_RT,
IOPRIO_CLASS_BE,
IOPRIO_CLASS_IDLE,
};
enum {
IOPRIO_WHO_PROCESS = 1,
IOPRIO_WHO_PGRP,
IOPRIO_WHO_USER,
};
#define IOPRIO_CLASS_SHIFT 13
static inline int
ioprio_set (int which, int who, int ioprio_val)
{
return syscall (__NR_ioprio_set, which, who, ioprio_val);
}
static int
set_io_priority (int ioprio,
int ioclass)
{
return ioprio_set (IOPRIO_WHO_PROCESS, 0, ioprio | (ioclass << IOPRIO_CLASS_SHIFT));
}
static const gchar *
ioclass_to_string (int ioclass)
{
switch (ioclass) {
case IOPRIO_CLASS_IDLE:
return "IDLE";
case IOPRIO_CLASS_BE:
return "BE";
default:
return "unknown";
}
}
/**
* gs_ioprio_set:
* @priority: I/O priority, with higher numeric values indicating lower priority;
* use %G_PRIORITY_DEFAULT as the default
*
* Set the I/O priority of the current thread using the `ioprio_set()` syscall.
*
* The @priority is quantised before being passed to the kernel.
*
* This function may fail if the process doesn’t have permission to change its
* I/O priority to the given value. If so, a warning will be printed, as the
* quantised priority values are chosen so they shouldn’t typically require
* permissions to set.
*/
void
gs_ioprio_set (gint priority)
{
int ioprio, ioclass;
/* If the priority is lower than default, use an idle I/O priority. The
* condition looks wrong because higher integers indicate lower priority
* in GLib.
*
* Otherwise use a default best-effort priority, which is the same as
* what all new threads get (in the absence of an I/O context with
* `CLONE_IO`). */
if (priority > G_PRIORITY_DEFAULT) {
ioprio = 7;
ioclass = IOPRIO_CLASS_IDLE;
} else if (priority == G_PRIORITY_DEFAULT) {
ioprio = 4; /* this is the default priority in the BE class */
ioclass = IOPRIO_CLASS_BE;
} else {
ioprio = 0; /* this is the highest priority in the BE class */
ioclass = IOPRIO_CLASS_BE;
}
g_debug ("Setting I/O priority of thread %p to %s, %d",
g_thread_self (), ioclass_to_string (ioclass), ioprio);
if (set_io_priority (ioprio, ioclass) == -1) {
g_warning ("Could not set I/O priority to %s, %d",
ioclass_to_string (ioclass), ioprio);
/* If we were trying to set to idle priority, try again with the
* lowest-possible best-effort priority. This is because kernels
* older than 2.6.25 required `CAP_SYS_ADMIN` to set
* `IOPRIO_CLASS_IDLE`. Newer kernels do not. */
if (ioclass == IOPRIO_CLASS_IDLE) {
ioprio = 7; /* this is the lowest priority in the BE class */
ioclass = IOPRIO_CLASS_BE;
if (set_io_priority (ioprio, ioclass) == -1)
g_warning ("Could not set best effort IO priority either, giving up");
}
}
}
#else /* __linux__ */
void
gs_ioprio_set (gint priority)
{
}
#endif /* __linux__ */
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