Hi Lukasz, On Tue, Oct 9, 2018 at 12:36 PM Lukasz Luba <[email protected]> wrote: > > PROVE_LOCKING enables LOCKDEP, which causes big overhead on cache and > bus transactions. > > On some ARM big.LITTLE architecutres (Exynos 5433) the overhead is really big. > The overhead can be measures using hackbench which will speed up > by x3 times (11sec -> 3.4sec). > When you check transaction on cache or buses, the results are way higher > than normal for the same hackbench test: > L1d cache invalidations: 26mln vs 4mln > L2u cache invalidations: 42mln vs 12mln > bus cyc/access: 30cyc/access vs. 20cyc/access > context switch is x3 times cheaper > > Enable this option only when you have some locking issue to investigate. > > Signed-off-by: Lukasz Luba <[email protected]> > --- > arch/arm/configs/imx_v6_v7_defconfig | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/arm/configs/imx_v6_v7_defconfig > b/arch/arm/configs/imx_v6_v7_defconfig > index 7eca43f..f55cd2d 100644 > --- a/arch/arm/configs/imx_v6_v7_defconfig > +++ b/arch/arm/configs/imx_v6_v7_defconfig > @@ -425,7 +425,6 @@ CONFIG_PRINTK_TIME=y > CONFIG_DEBUG_FS=y > CONFIG_MAGIC_SYSRQ=y > # CONFIG_SCHED_DEBUG is not set > -CONFIG_PROVE_LOCKING=y
Russell explains here why it is desirable to have CONFIG_PROVE_LOCKING=y for development: https://www.spinics.net/lists/kernel/msg2929513.html
