* Al Boldi <[EMAIL PROTECTED]> wrote: > > so could you please re-check chew jitter behavior with the latest > > kernel? (i've attached the standalone patch below, it will apply > > cleanly to rc2 too.) > > That fixes it, but by reducing granularity ctx is up 4-fold.
ok, great! (the context-switch rate is obviously up.) > Mind you, it does have an enormous effect on responsiveness, as > negative nice with small granularity can't hijack the system any more. ok. i'm glad you like the result :-) This makes reniced X (or any reniced app) more usable. > The thing is, this unpredictability seems to exist even at nice level > 0, but the smaller granularity covers it all up. It occasionally > exhibits itself as hick-ups during transient heavy workload flux. But > it's not easily reproducible. In general, "hickups" can be due to many, many reasons. If a task got indeed delayed by scheduling jitter that is provable, even if the behavior is hard to reproduce, by enabling CONFIG_SCHED_DEBUG=y and CONFIG_SCHEDSTATS=y in your kernel. First clear all the stats: for N in /proc/*/task/*/sched; do echo 0 > $N; done then wait for the 'hickup' to happen, and once it happens capture the system state (after the hickup) via this script: http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh and tell me which specific task exhibited that 'hickup' and send me the debug output. Also, could you try the patch below as well? Thanks, Ingo --------------------------------> Subject: sched: fix sleeper bonus From: Ingo Molnar <[EMAIL PROTECTED]> Peter Ziljstra noticed that the sleeper bonus deduction code was not properly rate-limited: a task that scheduled more frequently would get a disproportionately large deduction. So limit the deduction to delta_exec. Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]> --- kernel/sched_fair.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) Index: linux/kernel/sched_fair.c =================================================================== --- linux.orig/kernel/sched_fair.c +++ linux/kernel/sched_fair.c @@ -75,7 +75,7 @@ enum { unsigned int sysctl_sched_features __read_mostly = SCHED_FEAT_FAIR_SLEEPERS *1 | - SCHED_FEAT_SLEEPER_AVG *1 | + SCHED_FEAT_SLEEPER_AVG *0 | SCHED_FEAT_SLEEPER_LOAD_AVG *1 | SCHED_FEAT_PRECISE_CPU_LOAD *1 | SCHED_FEAT_START_DEBIT *1 | @@ -304,11 +304,9 @@ __update_curr(struct cfs_rq *cfs_rq, str delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw); if (cfs_rq->sleeper_bonus > sysctl_sched_granularity) { - delta = calc_delta_mine(cfs_rq->sleeper_bonus, - curr->load.weight, lw); - if (unlikely(delta > cfs_rq->sleeper_bonus)) - delta = cfs_rq->sleeper_bonus; - + delta = min(cfs_rq->sleeper_bonus, (u64)delta_exec); + delta = calc_delta_mine(delta, curr->load.weight, lw); + delta = min((u64)delta, cfs_rq->sleeper_bonus); cfs_rq->sleeper_bonus -= delta; delta_mine -= delta; } @@ -521,6 +519,8 @@ static void __enqueue_sleeper(struct cfs * Track the amount of bonus we've given to sleepers: */ cfs_rq->sleeper_bonus += delta_fair; + if (unlikely(cfs_rq->sleeper_bonus > sysctl_sched_runtime_limit)) + cfs_rq->sleeper_bonus = sysctl_sched_runtime_limit; schedstat_add(cfs_rq, wait_runtime, se->wait_runtime); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
