[PATCH 3/5] sched-make_task_noninteractive_use_sleep_type.patch

[Con Kolivas]

Alterations to the pipe code in the kernel made it possible for relative
starvation to occur with tasks that slept waiting on a pipe getting
unfair priority bonuses even if they were otherwise fully cpu bound so the
TASK_NONINTERACTIVE flag was introduced which prevented any change to
sleep_avg while sleeping waiting on a pipe. This change also leads to the
converse though, preventing any priority boost from occurring in truly
interactive tasks that wait on pipes.

Convert the TASK_NONINTERACTIVE flag to set sleep_type to
SLEEP_NONINTERACTIVE which will allow a linear bonus to priority based on
sleep time thus allowing interactive tasks to get high priority if they
sleep enough.

Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>

 kernel/sched.c |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)

Index: linux-2.6.15/kernel/sched.c
===================================================================
--- linux-2.6.15.orig/kernel/sched.c
+++ linux-2.6.15/kernel/sched.c
@@ -1348,18 +1348,18 @@ out_activate:
 		 * cpu bound so label them as noninteractive.
 		 */
 		p->sleep_type = SLEEP_NONINTERACTIVE;
-	}
+	} else
 
 	/*
 	 * 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.)
+	 * woken up with their sleep average not weighted in an
+	 * interactive way.
 	 */
-	if (old_state & TASK_NONINTERACTIVE)
-		__activate_task(p, rq);
-	else
-		activate_task(p, rq, cpu == this_cpu);
+		if (old_state & TASK_NONINTERACTIVE)
+			p->sleep_type = SLEEP_NONINTERACTIVE;
+
+
+	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)

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