[patch] TASK_NONINTERACTIVE (was: Machine Freezes while Running Crossover Office)

Ingo Molnar
2005-06-01T07:39:12Z

Pekka, could you check whether the patch below solves your Wine problem
(without hurting interactivity otherwise)?

Ingo

----

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>

--- linux/fs/pipe.c.orig
+++ linux/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);
--- linux/kernel/sched.c.orig
+++ linux/kernel/sched.c
@@ -1085,6 +1085,16 @@ 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
@@ -1092,7 +1102,6 @@ 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);
--- linux/include/linux/sched.h.orig
+++ linux/include/linux/sched.h
@@ -112,6 +112,7 @@ 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)