[PATCH] sched: TASK_NONINTERACTIVE

This patch implements a task state bit (TASK_NONINTERACTIVE), which can be
used by blocking points to mark the task's wait as "non-interactive".  This
does not mean the task will be considered a CPU-hog - the wait will simply
not have an effect on the waiting task's priority - positive or negative
alike.  Right now only pipe_wait() will make use of it, because it's a
common source of not-so-interactive waits (kernel compilation jobs, etc.).

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/pipe.c b/fs/pipe.c
index 2c7a23d..66aa0b9 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -39,7 +39,11 @@ void pipe_wait(struct inode * inode)
 {
        DEFINE_WAIT(wait);
 
-       prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE);
+       /*
+        * Pipes are system-local resources, so sleeping on them
+        * is considered a noninteractive wait:
+        */
+       prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE|TASK_NONINTERACTIVE);
        up(PIPE_SEM(*inode));
        schedule();
        finish_wait(PIPE_WAIT(*inode), &wait);

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8a1fcfe..ac70f84 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -114,6 +114,7 @@ extern unsigned long nr_iowait(void);
 #define TASK_TRACED            8
 #define EXIT_ZOMBIE            16
 #define EXIT_DEAD              32
+#define TASK_NONINTERACTIVE    64
 
 #define __set_task_state(tsk, state_value)             \
        do { (tsk)->state = (state_value); } while (0)

diff --git a/kernel/sched.c b/kernel/sched.c
index 24eed37..6da13bb 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1261,6 +1261,16 @@ out_activate:
        }
 
        /*
+        * Tasks that have marked their sleep as noninteractive get
+        * woken up without updating their sleep average. (i.e. their
+        * sleep is handled in a priority-neutral manner, no priority
+        * boost and no penalty.)
+        */
+       if (old_state & TASK_NONINTERACTIVE)
+               __activate_task(p, rq);
+       else
+               activate_task(p, rq, cpu == this_cpu);
+       /*
         * Sync wakeups (i.e. those types of wakeups where the waker
         * has indicated that it will leave the CPU in short order)
         * don't trigger a preemption, if the woken up task will run on
@@ -1268,7 +1278,6 @@ out_activate:
         * the waker guarantees that the freshly woken up task is going
         * to be considered on this CPU.)
         */
-       activate_task(p, rq, cpu == this_cpu);
        if (!sync || cpu != this_cpu) {
                if (TASK_PREEMPTS_CURR(p, rq))
                        resched_task(rq->curr);