On 10/27/23 09:40, Feng Tang wrote: > On Fri, Oct 20, 2023 at 10:21:28PM +0800, Sang, Oliver wrote: >> >> >> Hello, >> >> kernel test robot noticed a -3.7% regression of will-it-scale.per_process_ops on: > > I was surprised to see this initially, as I know this patch which > only affects the order of a few slabs in a certain size range, and > 0Day has enabled the 64 bytes alignment for function address. > > One only big difference of perf hot spot is > >> 19.62 +1.9 21.54 perf-profile.self.cycles-pp.__fget_light > > but its code flow and data doesn't have much to do with the commit. > > I manually run the test case, and didn't see the affected slabs > actively used by checking 'slabtop' > > Then I hacked to move slub.c to a very late position when linking > kernel image, so that very few other kernel modules' alignment will > be affected, and the regression is gone. > > So this seems to be another strange perf change caused by text code > alignment changes. similar to another recent case of MCE patch > https://lore.kernel.org/lkml/202310111637.dee70328-oliver.sang@xxxxxxxxx/ I suspected it would be something like this, thanks for confirming!
