[POWERPC] spusched: Disable tick when not needed

Only enable the scheduler tick if we have any context waiting to be
scheduled.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 10 insertions, 8 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index bb16c22360d5..2fb0e63344cc 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -294,9 +294,10 @@ static void __spu_add_to_rq(struct spu_context *ctx)
 {
         int prio = ctx->prio;
 
-        spu_prio->nr_waiting++;
         list_add_tail(&ctx->rq, &spu_prio->runq[prio]);
         set_bit(prio, spu_prio->bitmap);
+        if (!spu_prio->nr_waiting++)
+                __mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
 }
 
 static void __spu_del_from_rq(struct spu_context *ctx)
@@ -304,11 +305,13 @@ static void __spu_del_from_rq(struct spu_context *ctx)
         int prio = ctx->prio;
 
         if (!list_empty(&ctx->rq)) {
+                if (!--spu_prio->nr_waiting)
+                        del_timer(&spusched_timer);
                 list_del_init(&ctx->rq);
-                spu_prio->nr_waiting--;
+
+                if (list_empty(&spu_prio->runq[prio]))
+                        clear_bit(prio, spu_prio->bitmap);
         }
-        if (list_empty(&spu_prio->runq[prio]))
-                clear_bit(prio, spu_prio->bitmap);
 }
 
 static void spu_prio_wait(struct spu_context *ctx)
@@ -654,9 +657,6 @@ static int spusched_thread(void *unused)
         struct spu *spu, *next;
         int node;
 
-        setup_timer(&spusched_timer, spusched_wake, 0);
-        __mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
-
         while (!kthread_should_stop()) {
                 set_current_state(TASK_INTERRUPTIBLE);
                 schedule();
@@ -670,7 +670,6 @@ static int spusched_thread(void *unused)
                 }
         }
 
-        del_timer_sync(&spusched_timer);
         return 0;
 }
 
@@ -732,6 +731,8 @@ int __init spu_sched_init(void)
         }
         spin_lock_init(&spu_prio->runq_lock);
 
+        setup_timer(&spusched_timer, spusched_wake, 0);
+
         spusched_task = kthread_run(spusched_thread, NULL, "spusched");
         if (IS_ERR(spusched_task)) {
                 err = PTR_ERR(spusched_task);
@@ -762,6 +763,7 @@ void __exit spu_sched_exit(void)
 
         remove_proc_entry("spu_loadavg", NULL);
 
+        del_timer_sync(&spusched_timer);
         kthread_stop(spusched_task);
 
         for (node = 0; node < MAX_NUMNODES; node++) {