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Diffstat (limited to 'lib/gs-ioprio.c')
| -rw-r--r-- | lib/gs-ioprio.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/lib/gs-ioprio.c b/lib/gs-ioprio.c new file mode 100644 index 0000000..3a63d07 --- /dev/null +++ b/lib/gs-ioprio.c @@ -0,0 +1,197 @@ +/* -*- 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__ */ |