Set background system priority for the group scheduler.

Original commit from Philip Van Hoof. I modified it to only include the
headers we absolutely need.

Conflicts:

	tumblerd/tumbler-group-scheduler.c

3 files changed, 84 insertions, 1 deletions

diff --git a/tumblerd/tumbler-group-scheduler.c b/tumblerd/tumbler-group-scheduler.c
index 8429cfa..f133d90 100644
--- a/tumblerd/tumbler-group-scheduler.c
+++ b/tumblerd/tumbler-group-scheduler.c
@@ -94,6 +94,7 @@ struct _TumblerGroupScheduler
   GMutex      *mutex;
   GList       *requests;
   guint        group;
+  gboolean     prioritized;
 
   gchar       *name;
 };
@@ -150,6 +151,13 @@ tumbler_group_scheduler_init (TumblerGroupScheduler *scheduler)
   scheduler->mutex = g_mutex_new ();
   scheduler->requests = NULL;
 
+  /* Note that unless we convert this boolean to a TLS (thread-local), that
+   * we can only do this 'prioritized' flag with a thread-pool that is set to
+   * exclusive: because then the one thread keeps running until the pool is 
+   * freed. */
+
+  scheduler->prioritized = FALSE;
+
   /* allocate a pool with one thread for all requests */
   scheduler->pool = g_thread_pool_new (tumbler_group_scheduler_thread, 
                                        scheduler, 1, TRUE, NULL);
@@ -360,12 +368,18 @@ tumbler_group_scheduler_thread (gpointer data,
   GList                   *thumbnails;
   GList                   *lp;
   guint                    n;
-  guint                    i;
   gint                     error_code;
 
   g_return_if_fail (TUMBLER_IS_GROUP_SCHEDULER (scheduler));
   g_return_if_fail (request != NULL);
 
+  /* Set I/O priority for the exclusive ThreadPool's thread */
+  if (!scheduler->prioritized) 
+    {
+      tumbler_scheduler_thread_use_lower_priority ();
+      scheduler->prioritized = TRUE;
+    }
+
   /* notify others that we're starting to process this request */
   g_signal_emit_by_name (request->scheduler, "started", request->handle);
 
diff --git a/tumblerd/tumbler-scheduler.c b/tumblerd/tumbler-scheduler.c
index 897cbaf..2897e3d 100644
--- a/tumblerd/tumbler-scheduler.c
+++ b/tumblerd/tumbler-scheduler.c
@@ -22,10 +22,46 @@
 #include <config.h>
 #endif
 
+#ifdef HAVE_SCHED_H
+#include <sched.h>
+#endif
+#ifdef HAVE_LINUX_SCHED_H 
+#include <linux/sched.h>
+#endif
+#ifdef HAVE_SYSCALL_H
+#include <syscall.h> 
+#endif
+
 #include <tumbler/tumbler.h>
 
 #include <tumblerd/tumbler-scheduler.h>
 
+
+#define IOPRIO_CLASS_SHIFT 13
+
+#ifndef SCHED_IDLE
+#define SCHED_IDLE 5
+#endif
+
+
+
+enum
+{
+  IOPRIO_CLASS_NONE,
+  IOPRIO_CLASS_RT,
+  IOPRIO_CLASS_BE,
+  IOPRIO_CLASS_IDLE,
+};
+
+
+
+enum 
+{
+  IOPRIO_WHO_PROCESS = 1,
+  IOPRIO_WHO_PGRP,
+  IOPRIO_WHO_USER,
+};
+
 /* signal identifiers */
 enum
 {
@@ -252,3 +288,34 @@ tumbler_scheduler_request_compare (gconstpointer a,
 
   return request_b->handle - request_a->handle;
 }
+
+static int
+ioprio_set (int which, int who, int ioprio_val)
+{
+#if defined(__NR_ioprio_set) && defined(HAVE_SYS_SYSCALL_H)
+  return syscall (__NR_ioprio_set, which, who, ioprio_val);
+#else
+  return 0;
+#endif
+}
+
+
+void
+tumbler_scheduler_thread_use_lower_priority (void)
+{
+#ifdef HAVE_SCHED_H
+  struct sched_param sp;
+#endif
+  int                ioprio;
+  int                ioclass;
+
+  ioprio = 7; /* priority is ignored with idle class */
+  ioclass = IOPRIO_CLASS_IDLE << IOPRIO_CLASS_SHIFT;
+
+  ioprio_set (IOPRIO_WHO_PROCESS, 0, ioprio | ioclass);
+
+#ifdef HAVE_SCHED_H
+  if (sched_getparam (0, &sp) == 0) 
+    sched_setscheduler (0, SCHED_IDLE, &sp);
+#endif
+}
diff --git a/tumblerd/tumbler-scheduler.h b/tumblerd/tumbler-scheduler.h
index 733e5aa..db5445e 100644
--- a/tumblerd/tumbler-scheduler.h
+++ b/tumblerd/tumbler-scheduler.h
@@ -81,6 +81,8 @@ gint                     tumbler_scheduler_request_compare       (gconstpointer
                                                                   gconstpointer            b,
                                                                   gpointer                 user_data);
 
+void                     tumbler_scheduler_thread_use_lower_priority (void);
+
 struct _TumblerSchedulerRequest
 {
   TumblerThumbnailer **thumbnailers;