+Michal Hocko Message starts at https://lkml.kernel.org/r/20201207142204.GA18516@rlk On Mon, Dec 7, 2020 at 10:08 PM Hui Su <sh_def@xxxxxxx> wrote: > > On Mon, Dec 07, 2020 at 09:28:46AM -0800, Shakeel Butt wrote: > > On Mon, Dec 7, 2020 at 6:22 AM Hui Su <sh_def@xxxxxxx> wrote: > > > > The reason to keep __memcg_kmem_[un]charge_page functions is that they > > were called in the very hot path. Can you please check the performance > > impact of your change and if the generated code is actually same or > > different. > > Hi, Shakeel: > > I objdump the mm/page_alloc.o and comapre them, it change the assemble code > indeed. In fact, it change some code order, which i personally think won't have > impact on performance. And i ran the ltp mm and conatiner test, it seems nothing > abnormal. Did you run the tests in a memcg? The change is behind a static key of kmem accounting which is enabled for subcontainers. > > BUT i still want to check whether this change will have negative impact on > perforance due to this change code was called in the very hot path like you > said, AND saddly i did not find a way to quantify the impact on performance. > Can you give me some suggestion about how to quantify the performance or some > tool? > At least I think we can try with a simple page allocation in a loop i.e. alloc_page(GFP_KERNEL_ACCOUNT). I will think of any existing benchmark which exercises this code path. Michal, do you have any suggestions?
