On Fri, Oct 20, 2023 at 11:46:36AM +0900, Hyeonggon Yoo wrote: > On Fri, Oct 20, 2023 at 10:27 AM Luiz Capitulino <luizcap@xxxxxxxxxx> wrote: > > > > Hi, > > > > As reported before[1], we found another regression in 6.1 when doing > > performance comparisons with 5.10. This one is caused by CONFIG_DEBUG_PREEMPT > > being enabled by default by the following upstream commit if you have the > > right config dependencies enabled (commit is introduced in v5.16-rc1): > > > > """ > > commit c597bfddc9e9e8a63817252b67c3ca0e544ace26 > > Author: Frederic Weisbecker <frederic@xxxxxxxxxx> > > Date: Tue Sep 14 12:31:34 2021 +0200 > > > > sched: Provide Kconfig support for default dynamic preempt mode > > """ > > > > We found up to 8% performance improvement with CONFIG_DEBUG_PREEMPT > > disabled in different perf benchmarks (including UnixBench process > > creation and redis). The root cause is explained in the commit log > > below which is merged in 6.3 and applies (almost) clealy on 6.1.59. > > Oh, I should've sent it to the stable. Thanks for sending it! > > Yes, DEBUG_PREEMPT was unintentionally enabled after the introduction > of PREEMPT_DYNAMIC. It was already enabled by default for PREEMPTION=y kernels > but PREEMPT_DYNAMIC always enables PREEMPT_BUILD (and hence PREEMPTION) > so distros that were using PREEMPT_VOLUNTARY are silently affected by that. > > It looks appropriate to be backported to the stable tree (to me). > Hmm but I think it should be backported to 5.15 too? Now queued up, thanks. greg k-h
