Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH v3 tip/core/rcu 14/18] rcu: Enable RCU tracepoints by default to aid in debugging | Date | Tue, 24 Jan 2017 13:51:25 -0800 |
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From: Matt Fleming <matt@codeblueprint.co.uk>
While debugging a performance issue I needed to understand why RCU sofitrqs were firing so frequently.
Unfortunately, the RCU callback tracepoints are hidden behind CONFIG_RCU_TRACE which defaults to off in the upstream kernel and is likely to also be disabled in enterprise distribution configs.
Enable it by default for CONFIG_TREE_RCU. However, we must keep it disabled for tiny RCU, because it would otherwise pull in a large amount of code that would make tiny RCU less than tiny.
I ran some file system metadata intensive workloads (git checkout, FS-Mark) on a variety of machines with this patch and saw no detectable change in performance.
Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> --- lib/Kconfig.debug | 1 + 1 file changed, 1 insertion(+)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index b06848a104e6..5655bd95919a 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1450,6 +1450,7 @@ config RCU_CPU_STALL_TIMEOUT config RCU_TRACE bool "Enable tracing for RCU" depends on DEBUG_KERNEL + default y if TREE_RCU select TRACE_CLOCK help This option provides tracing in RCU which presents stats -- 2.5.2
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