From: Matt Fleming Date: Fri, 23 Dec 2016 15:17:53 +0000 (+0000) Subject: rcu: Enable RCU tracepoints by default to aid in debugging X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=961518259b3b;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git rcu: Enable RCU tracepoints by default to aid in debugging 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 Signed-off-by: Matt Fleming Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- 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