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. > > 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. > > Regards, > > Tony Regards, Lukasz
