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Wed, 21 Aug 2024 15:01:30 -0700 (PDT) MIME-Version: 1.0 References: <20240811224940.39876-1-21cnbao@gmail.com> <20240811224940.39876-3-21cnbao@gmail.com> <6c01b794-7c51-4d90-a215-210ac21401d2@redhat.com> In-Reply-To: <6c01b794-7c51-4d90-a215-210ac21401d2@redhat.com> From: Barry Song <21cnbao@gmail.com> Date: Thu, 22 Aug 2024 06:01:17 +0800 Message-ID: Subject: Re: [PATCH v2 2/2] mm: collect the number of anon large folios on split_deferred list To: David Hildenbrand Cc: akpm@linux-foundation.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, chrisl@kernel.org, hanchuanhua@oppo.com, ioworker0@gmail.com, kaleshsingh@google.com, kasong@tencent.com, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, v-songbaohua@oppo.com, ziy@nvidia.com, yuanshuai@oppo.com, Usama Arif Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 562A51C000A X-Stat-Signature: 1mxtgd3sxo96r3tuy5f3ybea4qrbx6in X-Rspam-User: X-HE-Tag: 1724277691-800612 X-HE-Meta: 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 b6Kc+dFe 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001140, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 22, 2024 at 5:39=E2=80=AFAM David Hildenbrand wrote: > > On 12.08.24 00:49, Barry Song wrote: > > From: Barry Song > > > > When an mTHP is added to the deferred_list, its partial pages > > are unused, leading to wasted memory and potentially increasing > > memory reclamation pressure. > > > > Detailing the specifics of how unmapping occurs is quite difficult > > and not that useful, so we adopt a simple approach: each time an > > mTHP enters the deferred_list, we increment the count by 1; whenever > > it leaves for any reason, we decrement the count by 1. > > > > Signed-off-by: Barry Song > > --- > > Documentation/admin-guide/mm/transhuge.rst | 5 +++++ > > include/linux/huge_mm.h | 1 + > > mm/huge_memory.c | 6 ++++++ > > 3 files changed, 12 insertions(+) > > > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation= /admin-guide/mm/transhuge.rst > > index 9fdfb46e4560..7072469de8a8 100644 > > --- a/Documentation/admin-guide/mm/transhuge.rst > > +++ b/Documentation/admin-guide/mm/transhuge.rst > > @@ -532,6 +532,11 @@ nr_anon > > These huge pages could be entirely mapped or have partially > > unmapped/unused subpages. > > > > +nr_split_deferred > > + the number of anon huge pages which have been partially unmappe= d > > + and put onto split queue. Those unmapped subpages are also unus= ed > > + and temporarily wasting memory. > > The name suggests something else ... like a counter of how many have > been deferred split :) > > Would "nr_anon_partially_mapped" "nr_anon_split_pending" (or something > less mouthful) be clearer? > > (likely "anon" really should be part of the name in any case) > > The name we chose (and the implied semantics) will likely have > implications on the handling of Usamas series. > Hi David, Your point is quite similar to my V1, though not exactly the same. I aimed = to make the name more meaningful for users. https://lore.kernel.org/all/20240808010457.228753-3-21cnbao@gmail.com/ Ryan felt that the name should be consistent with the existing split_deferr= ed. https://lore.kernel.org/all/36e8f1be-868d-4bce-8f32-e2d96b8b7af3@arm.com/#t It seems that the existing split_deferred may now be less optimal with Usama's series, as entirely_mapped folios might also be on the list. Ryan is out right now, but I suppose he will be convinced that "nr_anon_partially_mapped" is probably a better name once he returns and reviews Usama's series. :-) > -- > Cheers, > > David / dhildenb > Thanks Barry