On Tue, Jul 4, 2023 at 12:22 AM Yin, Fengwei <fengwei.yin@xxxxxxxxx> wrote: > > On 7/4/2023 10:18 AM, Yu Zhao wrote: > > On Mon, Jul 3, 2023 at 7:53 AM Ryan Roberts <ryan.roberts@xxxxxxx> wrote: > >> > >> Hi All, > >> > >> This is v2 of a series to implement variable order, large folios for anonymous > >> memory. The objective of this is to improve performance by allocating larger > >> chunks of memory during anonymous page faults. See [1] for background. > > > > Thanks for the quick response! > > > >> I've significantly reworked and simplified the patch set based on comments from > >> Yu Zhao (thanks for all your feedback!). I've also renamed the feature to > >> VARIABLE_THP, on Yu's advice. > >> > >> The last patch is for arm64 to explicitly override the default > >> arch_wants_pte_order() and is intended as an example. If this series is accepted > >> I suggest taking the first 4 patches through the mm tree and the arm64 change > >> could be handled through the arm64 tree separately. Neither has any build > >> dependency on the other. > >> > >> The one area where I haven't followed Yu's advice is in the determination of the > >> size of folio to use. It was suggested that I have a single preferred large > >> order, and if it doesn't fit in the VMA (due to exceeding VMA bounds, or there > >> being existing overlapping populated PTEs, etc) then fallback immediately to > >> order-0. It turned out that this approach caused a performance regression in the > >> Speedometer benchmark. > > > > I suppose it's regression against the v1, not the unpatched kernel. > From the performance data Ryan shared, it's against unpatched kernel: > > Speedometer 2.0: > > | kernel | runs_per_min | > |:-------------------------------|---------------:| > | baseline-4k | 0.0% | > | anonfolio-lkml-v1 | 0.7% | > | anonfolio-lkml-v2-simple-order | -0.9% | > | anonfolio-lkml-v2 | 0.5% | I see. Thanks. A couple of questions: 1. Do we have a stddev? 2. Do we have a theory why it regressed? Assuming no bugs, I don't see how a real regression could happen -- falling back to order-0 isn't different from the original behavior. Ryan, could you `perf record` and `cat /proc/vmstat` and share them?
