Re: [PATCH 1/1] sched: Make schedstats a runtime tunable that is disabled by default v4

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

> Changelog since v3
> o Force enable stats during profiling and latencytop
> 
> Changelog since V2
> o Print stats that are not related to schedstat
> o Reintroduce a static inline for update_stats_dequeue
> 
> Changelog since V1
> o Introduce schedstat_enabled and address Ingo's feedback
> o More schedstat-only paths eliminated, particularly ttwu_stat
> 
> schedstats is very useful during debugging and performance tuning but it
> incurs overhead. As such, even though it can be disabled at build time,
> it is often enabled as the information is useful.  This patch adds a
> kernel command-line and sysctl tunable to enable or disable schedstats on
> demand. It is disabled by default as someone who knows they need it can
> also learn to enable it when necessary.
> 
> The benefits are workload-dependent but when it gets down to it, the
> difference will be whether cache misses are incurred updating the shared
> stats or not. These measurements were taken from a 48-core 2-socket machine
> with Xeon(R) E5-2670 v3 cpus although they were also tested on a single
> socket machine 8-core machine with Intel i7-3770 processors.
> 
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>

Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>


-- 
Thanks and Regards
Srikar Dronamraju