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Thu, 19 Sep 2024 18:24:08 -0700 (PDT) MIME-Version: 1.0 References: <20240914063746.46290-1-21cnbao@gmail.com> <92f97c8e-f23d-4c6e-9f49-230fb4e96c46@redhat.com> In-Reply-To: <92f97c8e-f23d-4c6e-9f49-230fb4e96c46@redhat.com> From: Barry Song <21cnbao@gmail.com> Date: Fri, 20 Sep 2024 13:23:57 +1200 Message-ID: Subject: Re: [PATCH RFC] mm: mglru: provide a separate list for lazyfree anon folios To: David Hildenbrand Cc: akpm@linux-foundation.org, linux-mm@kvack.org, mhocko@suse.com, fengbaopeng@honor.com, gaoxu2@honor.com, hailong.liu@oppo.com, kaleshsingh@google.com, linux-kernel@vger.kernel.org, lokeshgidra@google.com, ngeoffray@google.com, shli@fb.com, surenb@google.com, yipengxiang@honor.com, yuzhao@google.com, minchan@kernel.org, Barry Song Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: E3D874000E X-Stat-Signature: h1sk8163nknprrd8swdn9pekq8wbw53t X-HE-Tag: 1726795449-220962 X-HE-Meta: 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 uczyrPe4 BRn+G5WrioRBud/KWQGlfmsNsY2VqVWYkFjUkeLd22BSYWYryBzwn8aJ+YbH2eE8mGGcI2GUioqfKDsN64ZNt2s37h1W+16fpV6TdZHGh45QgtNEgckz4I+OC53WvFy36bXCUrSbtcAT17t6y6AlGBL+X86QvEP1wWN+egA2LzIyIrA68+d7XBI/7IIOI+arK2X3Vlh8FybKJdR++Hmo/QetdDXPe8K/x8OC77+r5dhE6z3xg8UwtP6kLjcyWHd3ElfBmqGjzVrZiEyKEhdHfmJUyM+be7GXjnoASsETkMD6pWSR9CmfQ4GuiVDPX4zmuH7g3ymF85bOdmXjQLcdqz+TJ/9p30bPEskIJNGCobrLbIMNiXeLD6xJiOg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000407, 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 Wed, Sep 18, 2024 at 12:02=E2=80=AFAM David Hildenbrand wrote: > > On 14.09.24 08:37, Barry Song wrote: > > From: Barry Song > > > > This follows up on the discussion regarding Gaoxu's work[1]. It's > > unclear if there's still interest in implementing a separate LRU > > list for lazyfree folios, but I decided to explore it out of > > curiosity. > > > > According to Lokesh, MADV_FREE'd anon folios are expected to be > > released earlier than file folios. One option, as implemented > > by Gao Xu, is to place lazyfree anon folios at the tail of the > > file's `min_seq` generation. However, this approach results in > > lazyfree folios being released in a LIFO manner, which conflicts > > with LRU behavior, as noted by Michal. > > > > To address this, this patch proposes maintaining a separate list > > for lazyfree anon folios while keeping them classified under the > > "file" LRU type to minimize code changes. These lazyfree anon > > folios will still be counted as file folios and share the same > > generation with regular files. In the eviction path, the lazyfree > > list will be prioritized for scanning before the actual file > > LRU list. > > > > What's the downside of another LRU list? Do we have any experience on tha= t? Essentially, the goal is to address the downsides of using a single LRU lis= t for files and lazyfree anonymous pages - seriously more files re-faults. I'm not entirely clear on the downsides of having an additional LRU list. While it does increase complexity, it doesn't seem to be significant. Let's wait for Gaoxu's test results before deciding on the next steps. I was just curious about how difficult it would be to add a separate list, so I took two hours to explore it :-) > > -- > Cheers, > > David / dhildenb > Thanks Barry