Messages in this thread | | | Subject | Re: [RFC v2 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on | From | Yang Shi <> | Date | Tue, 24 Apr 2018 07:08:36 -0600 |
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On 4/24/18 6:43 AM, Michal Hocko wrote: > On Mon 23-04-18 21:41:50, Yang Shi wrote: >> >> On 4/23/18 9:04 AM, Michal Hocko wrote: >>> On Sun 22-04-18 21:28:59, Yang Shi wrote: >>>> On 4/22/18 6:47 PM, Michal Hocko wrote: >>> [...] >>>>> will be used on the first aligned address even when the initial/last >>>>> portion of the mapping is not THP aligned. >>>> No, my test shows it is not. And, transhuge_vma_suitable() does check the >>>> virtual address alignment. If it is not huge page size aligned, it will not >>>> set PMD for huge page. >>> It's been quite some time since I've looked at that code but I think you >>> are wrong. It just doesn't make sense to make the THP decision on the >>> VMA alignment much. Kirill, can you clarify please? >> Thanks a lot Michal and Kirill to elaborate how tmpfs THP make pmd map. >> >> I did a quick test, THP will be PMD mapped as long as : >> * hint address is huge page aligned if MAP_FIXED >> Or >> * offset is huge page aligned >> And >> * The size is big enough (>= huge page size) >> >> This test does verify what Kirill said. And, I dig into a little further >> qemu code and did strace, qemu does try to mmap the file to non huge page >> aligned address with MAP_FIXED. > Does it make sense to contact Qemu developers and probably fix this?
Yes, I think so. We can submit a bug report to QEMU.
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