Messages in this thread | | | Date | Mon, 13 Nov 2023 20:59:37 +0800 | Subject | Re: [RFC PATCH] mm: support large folio numa balancing | From | Baolin Wang <> |
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On 11/13/2023 6:53 PM, David Hildenbrand wrote: > On 13.11.23 11:45, Baolin Wang wrote: >> Currently, the file pages already support large folio, and supporting for >> anonymous pages is also under discussion[1]. Moreover, the numa balancing >> code are converted to use a folio by previous thread[2], and the >> migrate_pages >> function also already supports the large folio migration. >> >> So now I did not see any reason to continue restricting NUMA balancing >> for >> large folio. > > I recall John wanted to look into that. CCing him. > > I'll note that the "head page mapcount" heuristic to detect sharers will > now strike on the PTE path and make us believe that a large folios is > exclusive, although it isn't. > > As spelled out in the commit you are referencing: > > commit 6695cf68b15c215d33b8add64c33e01e3cbe236c > Author: Kefeng Wang <wangkefeng.wang@huawei.com> > Date: Thu Sep 21 15:44:14 2023 +0800 > > mm: memory: use a folio in do_numa_page() > Numa balancing only try to migrate non-compound page in > do_numa_page(), > use a folio in it to save several compound_head calls, note we use > folio_estimated_sharers(), it is enough to check the folio sharers > since > only normal page is handled, if large folio numa balancing is > supported, a > precise folio sharers check would be used, no functional change > intended.
Thanks for pointing out the part I missed.
I saw the migrate_pages() syscall is also using folio_estimated_sharers() to check if the folio is shared, and I wonder it will bring about any significant issues?
> I'll send WIP patches for one approach that can improve the situation > soonish.
Great. Look forward to seeing this:)
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