From: Yang Shi <shy828301@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Song Liu <songliubraving@fb.com>,
Rik van Riel <riel@surriel.com>, Zi Yan <ziy@nvidia.com>,
"Theodore Ts'o" <tytso@mit.edu>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [v3 PATCH 0/8] Make khugepaged collapse readonly FS THP more consistent
Date: Wed, 27 Apr 2022 16:16:41 -0700 [thread overview]
Message-ID: <CAHbLzkpH6zRtgBZixVsvMnO8Y+fM74dTAP=ktqS_bBUrsNz8qg@mail.gmail.com> (raw)
In-Reply-To: <YmmuivdOWcr46oNC@casper.infradead.org>
On Wed, Apr 27, 2022 at 1:59 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Apr 04, 2022 at 05:48:49PM -0700, Yang Shi wrote:
> > When khugepaged collapses file THPs, its behavior is not consistent.
> > It is kind of "random luck" for khugepaged to see the file vmas (see
> > report: https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@suse.cz/)
> > since currently the vmas are registered to khugepaged when:
> > - Anon huge pmd page fault
> > - VMA merge
> > - MADV_HUGEPAGE
> > - Shmem mmap
> >
> > If the above conditions are not met, even though khugepaged is enabled
> > it won't see any file vma at all. MADV_HUGEPAGE could be specified
> > explicitly to tell khugepaged to collapse this area, but when
> > khugepaged mode is "always" it should scan suitable vmas as long as
> > VM_NOHUGEPAGE is not set.
>
> I don't see that as being true at all. The point of this hack was that
> applications which really knew what they were doing could enable it.
> It makes no sense to me that setting "always" by the sysadmin for shmem
> also force-enables ROTHP, even for applications which aren't aware of it.
>
> Most telling, I think, is that Song Liu hasn't weighed in on this at
> all. It's clearly not important to the original author.
Song Liu already acked the series, please see
https://lore.kernel.org/linux-mm/96F2D93B-2043-44C3-8062-C639372A0212@fb.com/
next prev parent reply other threads:[~2022-04-27 23:16 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-04 20:02 Yang Shi
2022-04-04 20:02 ` [v3 PATCH 1/8] sched: coredump.h: clarify the use of MMF_VM_HUGEPAGE Yang Shi
2022-05-09 12:25 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 2/8] mm: khugepaged: remove redundant check for VM_NO_KHUGEPAGED Yang Shi
2022-05-09 12:45 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 3/8] mm: khugepaged: skip DAX vma Yang Shi
2022-05-09 12:46 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 4/8] mm: thp: only regular file could be THP eligible Yang Shi
2022-05-09 13:41 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 5/8] mm: khugepaged: make khugepaged_enter() void function Yang Shi
2022-05-09 13:46 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 6/8] mm: khugepaged: move some khugepaged_* functions to khugepaged.c Yang Shi
2022-05-09 15:31 ` Vlastimil Babka
2022-05-09 23:00 ` Yang Shi
2022-04-04 20:02 ` [v3 PATCH 7/8] mm: khugepaged: introduce khugepaged_enter_vma() helper Yang Shi
2022-05-09 15:39 ` Vlastimil Babka
2022-04-04 20:02 ` [v3 PATCH 8/8] mm: mmap: register suitable readonly file vmas for khugepaged Yang Shi
2022-05-09 15:43 ` Vlastimil Babka
2022-04-05 0:16 ` [v3 PATCH 0/8] Make khugepaged collapse readonly FS THP more consistent Matthew Wilcox
2022-04-05 0:48 ` Yang Shi
2022-04-27 20:58 ` Matthew Wilcox
2022-04-27 22:38 ` Yang Shi
2022-04-27 23:16 ` Yang Shi [this message]
2022-05-09 16:05 ` Vlastimil Babka
2022-05-09 20:34 ` Yang Shi
2022-05-10 7:35 ` Vlastimil Babka
2022-05-10 19:25 ` Yang Shi
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