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References: <20240501042700.83974-1-ioworker0@gmail.com> <20240501160803.60988-1-sj@kernel.org>
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From: Lance Yang <ioworker0@gmail.com>
Date: Thu, 2 May 2024 08:30:39 +0800
Message-ID: <CAK1f24k1qcTUnaZ-ZoT7GWkpWk-vDUjVb+yL9QWZAvfSLxEsCQ@mail.gmail.com>
Subject: Re: [PATCH v4 0/3] Reclaim lazyfree THP without splitting
To: SeongJae Park <sj@kernel.org>
Cc: akpm@linux-foundation.org, willy@infradead.org, maskray@google.com, 
	ziy@nvidia.com, ryan.roberts@arm.com, david@redhat.com, 21cnbao@gmail.com, 
	mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, 
	shy828301@gmail.com, xiehuan09@gmail.com, libang.li@antgroup.com, 
	wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, 
	minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Thu, May 2, 2024 at 12:08=E2=80=AFAM SeongJae Park <sj@kernel.org> wrote=
:
>
> Hi Lance,
>
> On Wed,  1 May 2024 12:26:57 +0800 Lance Yang <ioworker0@gmail.com> wrote=
:
>
> > Hi all,
> >
> > This series adds support for reclaiming PMD-mapped THP marked as lazyfr=
ee
> > without needing to first split the large folio via split_huge_pmd_addre=
ss().
> >
> > When the user no longer requires the pages, they would use madvise(MADV=
_FREE)
> > to mark the pages as lazy free. Subsequently, they typically would not =
re-write
> > to that memory again.
> >
> > During memory reclaim, if we detect that the large folio and its PMD ar=
e both
> > still marked as clean and there are no unexpected references(such as GU=
P), so we
> > can just discard the memory lazily, improving the efficiency of memory
> > reclamation in this case.
> >
> > Performance Testing
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > On an Intel i5 CPU, reclaiming 1GiB of lazyfree THPs using
> > mem_cgroup_force_empty() results in the following runtimes in seconds
> > (shorter is better):
> >
> > --------------------------------------------
> > |     Old       |      New       |  Change  |
> > --------------------------------------------
> > |   0.683426    |    0.049197    |  -92.80% |
> > --------------------------------------------
> >
> > ---
> >
> > Changes since v3 [3]
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >  - mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop
> >     - Resolve compilation errors by handling the case where
> >       CONFIG_PGTABLE_HAS_HUGE_LEAVES is undefined (thanks to SeongJae P=
ark)
>
> I confirmed that the issue I reported before is disappeared with this ver=
sion
> of the patchset.  For the fix,
>
> Tested-by: SeongJae Park <sj@kernel.org>

Hey SJ,

Thanks for taking time to confirm! I appreciate your feedback!

Thanks,
Lance

>
>
> Thanks,
> SJ
>
> [...]