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AJvYcCU0LD5mAD2oEXNtcGAdnAhzyjZcUcbwodHKtD59j3g6mNKGTQEdRy116SO35wDpVZFZmml2vyMGNQ==@kvack.org X-Gm-Message-State: AOJu0YzZNjsI6UyKMYk0pvHxvkqGbHd9xaBQgATbW5r5prnTkJqcQUJO jvpMUELfpM065VneNmDVo/RFPUc03CBDrjIeladL1myH5IrHnNrr9qEaAEJLcL29TGIbvcnWKxf /v+rYIEK0WKY9z/Z+O21oj5r9MtA= X-Gm-Gg: ASbGnct585woPNBBqzDnndB1440Mk1xNODrP2onjoLxBo7o304iZwDjh0SUcvFD7Fg0 D/zUK1uu0yv9sCVUnk6GG+fumagJFbsTzrRSINIM= X-Google-Smtp-Source: AGHT+IFeP/0vYFVff+ko43d8W5hG2jzmDAJOPoSV/2Ia3Km3xVaOa6aGqs9rkpo+RFoGcHGxCIySFjTVwuXobAIAyK8= X-Received: by 2002:a05:6214:cca:b0:6d8:8f3d:4d82 with SMTP id 6a1803df08f44-6dc969a9b19mr119280226d6.46.1734232252887; Sat, 14 Dec 2024 19:10:52 -0800 (PST) MIME-Version: 1.0 References: <20241206083025.3478-1-laoar.shao@gmail.com> In-Reply-To: <20241206083025.3478-1-laoar.shao@gmail.com> From: Yafang Shao Date: Sun, 15 Dec 2024 11:10:17 +0800 Message-ID: Subject: Re: [PATCH v3] mm/readahead: fix large folio support in async readahead To: akpm@linux-foundation.org Cc: willy@infradead.org, david@redhat.com, oliver.sang@intel.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: iquopf6o9y64pi74bwtqzdtpn3bmro4u X-Rspamd-Queue-Id: AC4BC180004 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1734232225-759303 X-HE-Meta: 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 E3WuFuUR mTfq12oQ8jtMFKduztTVGFH1U3MI4+NjyycfOc9IectNAau9ood4/2GV1leDxeqcOb2rvbP+nVoa2td8XgZj73mzJ+/XMT/BGjTeaS0EKCGclbla72OoRWQXukl/vS7c7pu1exh+sil8f0EBH8hvk+PHquLEkdxcJ3t3Qrvch2Byf4xiETqv+FgWSe6ThqB2SdVaZFbbDJhUDAgnxAdi4SKozaHrpr2eRaawpHHj6qJmZ1wEnxeuoWQ9RC6c8I+sQOOvrWTeoxBEWgjLNHkcrDp0PY9HOE67C/buGFdv33zHamHoquBxmPk4IqbEGus4drtmTjnd9xAevj1iEGNEm/KjfB9jSN++CzjQJRnbqR6tKc3ODxSglL9Y/RaKRvSvs7UpbLNZfTZWyL2TNeU8r7oVp3+2Z5aRmsBK8EPAKOdOvX8J4e3cuHtE1/opt2sQUR6Es17Syhm+AitvhndYvqrPH5w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.011787, 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 Fri, Dec 6, 2024 at 4:31=E2=80=AFPM Yafang Shao w= rote: > > When testing large folio support with XFS on our servers, we observed tha= t > only a few large folios are mapped when reading large files via mmap. > After a thorough analysis, I identified it was caused by the > `/sys/block/*/queue/read_ahead_kb` setting. On our test servers, this > parameter is set to 128KB. After I tune it to 2MB, the large folio can > work as expected. However, I believe the large folio behavior should not > be dependent on the value of read_ahead_kb. It would be more robust if > the kernel can automatically adopt to it. > > With /sys/block/*/queue/read_ahead_kb set to 128KB and performing a > sequential read on a 1GB file using MADV_HUGEPAGE, the differences in > /proc/meminfo are as follows: > > - before this patch > FileHugePages: 18432 kB > FilePmdMapped: 4096 kB > > - after this patch > FileHugePages: 1067008 kB > FilePmdMapped: 1048576 kB > > This shows that after applying the patch, the entire 1GB file is mapped t= o > huge pages. The stable list is CCed, as without this patch, large folios > don't function optimally in the readahead path. > > It's worth noting that if read_ahead_kb is set to a larger value that > isn't aligned with huge page sizes (e.g., 4MB + 128KB), it may still fail > to map to hugepages. > > Link: https://lkml.kernel.org/r/20241108141710.9721-1-laoar.shao@gmail.co= m > Fixes: 4687fdbb805a ("mm/filemap: Support VM_HUGEPAGE for file mappings") > Signed-off-by: Yafang Shao > Tested-by: kernel test robot > Cc: Matthew Wilcox > Cc: David Hildenbrand > Cc: > --- > mm/readahead.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > Changes: > v2->v3: > - Fix the softlockup reported by kernel test robot > https://lore.kernel.org/linux-fsdevel/202411292300.61edbd37-lkp@intel.c= om/ > > v1->v2: https://lore.kernel.org/linux-mm/20241108141710.9721-1-laoar.shao= @gmail.com/ > - Drop the alignment (Matthew) > - Improve commit log (Andrew) > > RFC->v1: https://lore.kernel.org/linux-mm/20241106092114.8408-1-laoar.sha= o@gmail.com/ > - Simplify the code as suggested by Matthew > > RFC: https://lore.kernel.org/linux-mm/20241104143015.34684-1-laoar.shao@g= mail.com/ > > diff --git a/mm/readahead.c b/mm/readahead.c > index 3dc6c7a128dd..1dc3cffd4843 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -642,7 +642,11 @@ void page_cache_async_ra(struct readahead_control *r= actl, > 1UL << order); > if (index =3D=3D expected) { > ra->start +=3D ra->size; > - ra->size =3D get_next_ra_size(ra, max_pages); > + /* > + * In the case of MADV_HUGEPAGE, the actual size might ex= ceed > + * the readahead window. > + */ > + ra->size =3D max(ra->size, get_next_ra_size(ra, max_pages= )); > ra->async_size =3D ra->size; > goto readit; > } > -- > 2.43.5 > Andrew, could you please drop the previous version and apply this updated one instead? --=20 Regards Yafang