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Received: from 192.168.0.100(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X1gM7MC_1777182923 cluster:ay36) by smtp.aliyun-inc.com; Sun, 26 Apr 2026 13:55:23 +0800 Message-ID: Date: Sun, 26 Apr 2026 13:55:22 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported" To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ziy@nvidia.com, ljs@kernel.org, lance.yang@linux.dev, wangkefeng.wang@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 244F180008 X-Stat-Signature: yr84oo9f5jb3jrbk5pcdifibugxobh57 X-HE-Tag: 1777182931-919463 X-HE-Meta: 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 dKAMOIe+ tmS1UTgVHgen5MEiyPCRCOzdWTOEfdBZEXZcRxHPElmT3I65+sornJsDP9lWWJ1vpAjVDRJPPeHiD3NLI7eHu6YzRXAB+QF8FuhCbovb5tgwiBuCtSOkkOM43hxGqQEk0caHRPY46CatDrTI8I/O0mJkrQST4uumsE42tnCpOqRjcOU7xF8pomhNOO8wxuVMpFXqyFqVnaM64CCVcQgwOoxKDHVmCgjU9UdtE/G0wXta1/KYhQNGP7LHOwMa6P0tDv9mN8dUb0r/polotrxiGZZeL/m4bBjk/r5F/P8u/Pam5MtMoOsvY0Svui4+4t5zSb4veClytqui2m3A= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/26 9:20 PM, David Hildenbrand (Arm) wrote: > On 4/23/26 03:41, Baolin Wang wrote: >> This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c. >> >> Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to >> determine whether the shmem mount supports large folios. However, for anonymous >> shmem, whether it supports large folios can be dynamically configured via sysfs >> interfaces, so setting or not setting mapping_set_large_folios() during initialization >> cannot accurately reflect whether anonymous shmem actually supports large folios, >> which has already caused some confusion[1]. >> >> Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios() >> setting consistent across all mappings in the entire tmpfs mount. In other words, >> under the same tmpfs mount, after remount, we might end up with some mappings >> supporting large folios (calling mapping_set_large_folios()) while others don't. >> >> After some investigation, I found that the write performance regression addressed >> by commit 5a90c155defa has already been fixed by the following commit 665575cff098b >> ("filemap: move prefaulting out of hot write path"). See the following test data: >> >> Base: >> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s ) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) >> >> Base + revert 5a90c155defa: >> dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s) >> dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) >> >> The data is basically consistent with minor fluctuation noise. So we can now >> safely revert commit 5a90c155defa to set mapping_set_large_folios() for all >> shmem mounts unconditionally. >> >> [1] https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/ >> Signed-off-by: Baolin Wang >> --- >> Note: for more investigation and test data, see: >> https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/ > > > Maybe add that as > > Link: https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/ > > above? Sure. And I noticed that Andrew has already helped add this link. Thanks Andrew! > Acked-by: David Hildenbrand (Arm) Thanks.