From: Hugh Dickins <hughd@google.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
hughd@google.com, kirill.shutemov@linux.intel.com,
mhocko@suse.com, rientjes@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [v3 PATCH 2/2] mm: thp: fix false negative of shmem vma's THP eligibility
Date: Thu, 18 Jul 2019 15:06:50 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.1907181457150.2510@eggly.anvils> (raw)
In-Reply-To: <dd44eb2f-a982-bd0e-a1ed-ab3ecbf3fc91@suse.cz>
On Thu, 18 Jul 2019, Vlastimil Babka wrote:
> On 7/18/19 11:44 PM, Andrew Morton wrote:
> > On Wed, 19 Jun 2019 09:28:42 -0700 Yang Shi <yang.shi@linux.alibaba.com> wrote:
> >
> >>> Sorry for replying rather late, and not in the v2 thread, but unlike
> >>> Hugh I'm not convinced that we should include vma size/alignment in the
> >>> test for reporting THPeligible, which was supposed to reflect
> >>> administrative settings and madvise hints. I guess it's mostly a matter
> >>> of personal feeling. But one objective distinction is that the admin
> >>> settings and madvise do have an exact binary result for the whole VMA,
> >>> while this check is more fuzzy - only part of the VMA's span might be
> >>> properly sized+aligned, and THPeligible will be 1 for the whole VMA.
> >>
> >> I think THPeligible is used to tell us if the vma is suitable for
> >> allocating THP. Both anonymous and shmem THP checks vma size/alignment
> >> to decide to or not to allocate THP.
> >>
> >> And, if vma size/alignment is not checked, THPeligible may show "true"
> >> for even 4K mapping. This doesn't make too much sense either.
> >
> > This discussion seems rather inconclusive. I'll merge up the patchset
> > anyway. Vlastimil, if you think some changes are needed here then
> > please let's get them sorted out over the next few weeks?
>
> Well, Hugh did ack it, albeit without commenting on this part. I don't
> feel strongly enough about this for a nack.
Right, I had no further comment: Yang and I agreed one way round,
you thought the other way. I was more persuaded by Yang's 4kB
example than by what you wrote; but not hugely excited either way.
Hugh
next prev parent reply other threads:[~2019-07-18 22:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 4:43 [v3 PATCH 0/2] Fix false negative of shmem vma's THP eligibility Yang Shi
2019-06-13 4:44 ` [v3 PATCH 1/2] mm: thp: make transhuge_vma_suitable available for anonymous THP Yang Shi
2019-07-17 19:43 ` Hugh Dickins
2019-07-17 21:03 ` Yang Shi
2019-06-13 4:44 ` [v3 PATCH 2/2] mm: thp: fix false negative of shmem vma's THP eligibility Yang Shi
2019-06-19 12:12 ` Vlastimil Babka
2019-06-19 16:28 ` Yang Shi
2019-07-18 21:44 ` Andrew Morton
2019-07-18 21:52 ` Vlastimil Babka
2019-07-18 22:06 ` Hugh Dickins [this message]
2019-07-17 19:44 ` Hugh Dickins
2019-07-15 19:49 ` [v3 PATCH 0/2] Fix " Yang Shi
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