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Wed, 06 Nov 2024 22:02:22 -0800 (PST) MIME-Version: 1.0 References: <20241106092114.8408-1-laoar.shao@gmail.com> <20241106130318.91f05382d2c0bbd2be3abff5@linux-foundation.org> <20241106200653.17640c022a94e0eec9276326@linux-foundation.org> In-Reply-To: <20241106200653.17640c022a94e0eec9276326@linux-foundation.org> From: Yafang Shao Date: Thu, 7 Nov 2024 14:01:46 +0800 Message-ID: Subject: Re: [PATCH] mm/readahead: Fix large folio support in async readahead To: Andrew Morton Cc: willy@infradead.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3EF6F4001F X-Stat-Signature: ciidomqirqb1ms3bn9bi863yjhh91sjc X-HE-Tag: 1730959327-804707 X-HE-Meta: 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 2fSgoEDR 4AKwFbR+UoVX5ZUWmC6MIKmFqS/YeUCyOyLFNxpZYfSO6gpnLnLmlGXskezKhmvCJmqgq7sLoaBJhGKwPHiOtceBoiwKf9s2VPPcP3nsFntDYZokT5Dm2EtGhe9pY+jeepbTrRJrtjKxbgTEtAAdvN4G7NqvvQWUrdGAyCbg9sjlT9O3zV16HNaNX6joA//9RtsW/VjsBMyzhvRepZcoc2qY8+ZqZM7IjcpNt3V4zZemjqm82tXEvzVWXqxSqUKZI1U8TgSSH6u9Vwse1eAoM885yU9ulE5LMlQWP/8ROtrfPlN4j0LzEDKGYn45aQyZPkn+4Pp1WjQCBAeEOvVDWbuhFsqRokNZDl3bCpP20SHP7z58YVomGVHmPiKuabPm6Q+MSrh9PtMRpEUvofR4jt05htIJ0KWGqKojV3bzXrpVIiAJPmBbl1CyB5w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.002432, 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, Nov 7, 2024 at 12:06=E2=80=AFPM Andrew Morton wrote: > > On Thu, 7 Nov 2024 11:39:36 +0800 Yafang Shao wrot= e: > > > On Thu, Nov 7, 2024 at 5:03=E2=80=AFAM Andrew Morton wrote: > > > > > > On Wed, 6 Nov 2024 17:21:14 +0800 Yafang Shao = wrote: > > > > > > > When large folio support is enabled and read_ahead_kb is set to a s= maller > > > > value, ra->size (4MB) may exceed the maximum allowed size (e.g., 12= 8KB). To > > > > address this, we need to add a conditional check for such cases. Ho= wever, > > > > this alone is insufficient, as users might set read_ahead_kb to a l= arger, > > > > non-hugepage-aligned value (e.g., 4MB + 128KB). In these instances,= it is > > > > essential to explicitly align ra->size with the hugepage size. > > > > > > How much performance improvement is this likely to offer our users? > > > > The performance boost comes from enabling the use of hugepages > > directly. Previously, users were unable to leverage large folios as > > expected. With this change, however, large folios are now usable as > > intended. > > Thanks, but I was hoping for something quantitative. Some nice before- > and-after testing? How important/useful/impactful is this change? will improve the commit log. > > > This improvement addresses a critical need in services like AI > > inference, which benefit substantially from hugetlbfs. However, using > > hugetlbfs effectively within containerized environments can be > > challenging. To overcome this limitation, we explored large folios as > > a more flexible and production-friendly alternative. > > > > > IOW, should we consider backporting it? > > > > We should consider backporting this change. We've already backported > > it to our local 6.1.y kernel, where it's performing well. > > The Fixes tag should ensure it will be included in the stable kernel, r= ight? > > For most subsystems, yes. In MM an explicit cc:stable is needed. > Along with a changelog which permits readers to understand why a > backport is proposed. will add a cc:stable in the next version. --=20 Regards Yafang