From: Ingo Molnar <mingo@elte.hu>
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>
---
fs/pipe.c | 6 +++++-
include/linux/sched.h | 1 +
kernel/sched.c | 11 ++++++++++-
3 files changed, 16 insertions(+), 2 deletions(-)
diff -puN fs/pipe.c~sched-task_noninteractive fs/pipe.c
--- devel/fs/pipe.c~sched-task_noninteractive 2005-07-30 00:44:26.000000000 -0700
+++ devel-akpm/fs/pipe.c 2005-07-30 00:44:26.000000000 -0700
@@ -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 -puN include/linux/sched.h~sched-task_noninteractive include/linux/sched.h
--- devel/include/linux/sched.h~sched-task_noninteractive 2005-07-30 00:44:26.000000000 -0700
+++ devel-akpm/include/linux/sched.h 2005-07-30 00:44:26.000000000 -0700
@@ -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 -puN kernel/sched.c~sched-task_noninteractive kernel/sched.c
--- devel/kernel/sched.c~sched-task_noninteractive 2005-07-30 00:44:26.000000000 -0700
+++ devel-akpm/kernel/sched.c 2005-07-30 00:44:26.000000000 -0700
@@ -1263,6 +1263,16 @@ 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
@@ -1270,7 +1280,6 @@ 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);
_