* Lukasz Luba <l.luba@xxxxxxxxxxxxxxxxxxx> [181113 10:22]: > Hi Tony, > > On 11/8/18 5:59 PM, Tony Lindgren wrote: > > Hi, > > > > * Lukasz Luba <l.luba@xxxxxxxxxxxxxxxxxxx> [181009 08:36]: > >> 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. > > > > I'm all for this, but this disables also other less intrusive > > debug options. It used to be that we'd get locking issues merged > > into drivers and I think that's how it originally got enabled. > That's common reason for a few defconfigs in mainline. Actually looks like this does not change the DEBUG related options.. I must have done something wrong earlier, sorry. So applying into omap-for-v5.1/defconfig. > > So we should take a look which ones we can or want to keep. > > Or just disable CONFIG_DEBUG completely. > Ideally, the CI should try a few 'types' of configs, > generated based on the 'defconfig'. Some 'smart' script might > cut the debug options for an image for performance regression tests. > > > > For distros, that's multi_v7_defconfig nowadays for most part > > so I think most people using omap2plus_defconfig are developers > > working on various devices. Yes I think that's the case. Regards, Tony
