From 172e082a9111ea504ee34cbba26284a5ebdc53a7 Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Wed, 9 Sep 2009 15:41:37 +0200 Subject: [PATCH] sched: Re-tune the scheduler latency defaults to decrease worst-case latencies Reduce the latency target from 20 msecs to 5 msecs. Why? Larger latencies increase spread, which is good for scaling, but bad for worst case latency. We still have the ilog(nr_cpus) rule to scale up on bigger server boxes. Signed-off-by: Mike Galbraith Acked-by: Peter Zijlstra LKML-Reference: <1252486344.28645.18.camel@marge.simson.net> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index af325a382b1b..26fadb44250c 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -24,7 +24,7 @@ /* * Targeted preemption latency for CPU-bound tasks: - * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds) + * (default: 5ms * (1 + ilog(ncpus)), units: nanoseconds) * * NOTE: this latency value is not the same as the concept of * 'timeslice length' - timeslices in CFS are of variable length @@ -34,13 +34,13 @@ * (to see the precise effective timeslice length of your workload, * run vmstat and monitor the context-switches (cs) field) */ -unsigned int sysctl_sched_latency = 20000000ULL; +unsigned int sysctl_sched_latency = 5000000ULL; /* * Minimal preemption granularity for CPU-bound tasks: - * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds) + * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) */ -unsigned int sysctl_sched_min_granularity = 4000000ULL; +unsigned int sysctl_sched_min_granularity = 1000000ULL; /* * is kept at sysctl_sched_latency / sysctl_sched_min_granularity @@ -63,13 +63,13 @@ unsigned int __read_mostly sysctl_sched_compat_yield; /* * SCHED_OTHER wake-up granularity. - * (default: 5 msec * (1 + ilog(ncpus)), units: nanoseconds) + * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) * * This option delays the preemption effects of decoupled workloads * and reduces their over-scheduling. Synchronous workloads will still * have immediate wakeup/sleep latencies. */ -unsigned int sysctl_sched_wakeup_granularity = 5000000UL; +unsigned int sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; -- 2.20.1