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