* Al Boldi <[email protected]> wrote:
> > > The problem is that consecutive runs don't give consistent results
> > > and sometimes stalls. You may want to try that.
> >
> > well, there's a natural saturation point after a few hundred tasks
> > (depending on your CPU's speed), at which point there's no idle time
> > left. From that point on things get slower progressively (and the
> > ability of the shell to start new ping tasks is impacted as well),
> > but that's expected on an overloaded system, isnt it?
>
> Of course, things should get slower with higher load, but it should be
> consistent without stalls.
>
> To see this problem, make sure you boot into /bin/sh with the normal
> VGA console (ie. not fb-console). Then try each loop a few times to
> show different behaviour; loops like:
>
> # for ((i=0; i<3333; i++)); do ping 10.1 -A > /dev/null & done
>
> # for ((i=0; i<3333; i++)); do nice -99 ping 10.1 -A > /dev/null & done
>
> # { for ((i=0; i<3333; i++)); do
> ping 10.1 -A > /dev/null &
> done } > /dev/null 2>&1
>
> Especially the last one sometimes causes a complete console lock-up,
> while the other two sometimes stall then surge periodically.
ok. I think i might finally have found the bug causing this. Could you
try the fix below, does your webserver thread-startup test work any
better?
Ingo
--------------------------->
Subject: sched: fix startup penalty calculation
From: Ingo Molnar <[email protected]>
fix task startup penalty miscalculation: sysctl_sched_granularity is
unsigned int and wait_runtime is long so we first have to convert it
to long before turning it negative ...
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched_fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -1048,7 +1048,7 @@ static void task_new_fair(struct rq *rq,
* -granularity/2, so initialize the task with that:
*/
if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
- p->se.wait_runtime = -(sysctl_sched_granularity / 2);
+ p->se.wait_runtime = -((long)sysctl_sched_granularity / 2);
__enqueue_entity(cfs_rq, se);
}
-
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