96 lines
3.5 KiB
Plaintext
96 lines
3.5 KiB
Plaintext
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From: Suresh Jayaraman <sjayaraman@suse.de>
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Subject: Revert sched latency defaults
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References: bnc#557307
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Patch-mainline: Never
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The upstream commit 172e082a91 re-tuned the sched latency defaults to better
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suit desktop workloads. This hurt server workloads. So revert the latency
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defaults to values similar to SLE11 GM to avoid several performance
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regressions.
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Also, turn FAIR_SLEEPERS off and NORMALIZED_SLEEPER on. The above scheduler
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tunables seem to be most effective with FAIR_SLEEPERS off and
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NORMALIZED_SLEEPER on.
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The sysbench, dbench and Specjjb results showed much better performance with
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these changes.
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The interbench results didn't show any user visible impact and I expect
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desktop workloads won't be affected much. Iam not aware of/heard of any impact
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of this tuning that is affecting any specific workload.
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Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
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---
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kernel/sched_fair.c | 12 ++++++------
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kernel/sched_features.h | 4 ++--
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2 files changed, 8 insertions(+), 8 deletions(-)
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Index: linux-2.6.32-master/kernel/sched_fair.c
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===================================================================
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--- linux-2.6.32-master.orig/kernel/sched_fair.c
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+++ linux-2.6.32-master/kernel/sched_fair.c
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@@ -24,7 +24,7 @@
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/*
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* Targeted preemption latency for CPU-bound tasks:
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- * (default: 5ms * (1 + ilog(ncpus)), units: nanoseconds)
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+ * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* NOTE: this latency value is not the same as the concept of
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* 'timeslice length' - timeslices in CFS are of variable length
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@@ -34,13 +34,13 @@
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* (to see the precise effective timeslice length of your workload,
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* run vmstat and monitor the context-switches (cs) field)
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*/
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-unsigned int sysctl_sched_latency = 5000000ULL;
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+unsigned int sysctl_sched_latency = 20000000ULL;
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/*
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* Minimal preemption granularity for CPU-bound tasks:
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- * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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+ * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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-unsigned int sysctl_sched_min_granularity = 1000000ULL;
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+unsigned int sysctl_sched_min_granularity = 4000000ULL;
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/*
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* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
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@@ -63,13 +63,13 @@ unsigned int __read_mostly sysctl_sched_
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/*
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* SCHED_OTHER wake-up granularity.
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- * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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+ * (default: 5 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*/
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-unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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+unsigned int sysctl_sched_wakeup_granularity = 5000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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Index: linux-2.6.32-master/kernel/sched_features.h
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===================================================================
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--- linux-2.6.32-master.orig/kernel/sched_features.h
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+++ linux-2.6.32-master/kernel/sched_features.h
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@@ -3,7 +3,7 @@
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* considers the task to be running during that period. This gives it
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* a service deficit on wakeup, allowing it to run sooner.
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*/
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-SCHED_FEAT(FAIR_SLEEPERS, 1)
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+SCHED_FEAT(FAIR_SLEEPERS, 0)
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/*
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* Only give sleepers 50% of their service deficit. This allows
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@@ -17,7 +17,7 @@ SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
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* longer period, and lighter task an effective shorter period they
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* are considered running.
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*/
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-SCHED_FEAT(NORMALIZED_SLEEPER, 0)
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+SCHED_FEAT(NORMALIZED_SLEEPER, 1)
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/*
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* Place new tasks ahead so that they do not starve already running
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