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Thu, 23 Apr 2026 10:40:14 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 90F5A40561; Thu, 23 Apr 2026 10:46:39 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 23 Apr 2026 10:46:38 +0800 Message-ID: <5c915191-b477-40af-8d56-ba9f2c24c5ec@huawei.com> Date: Thu, 23 Apr 2026 10:46:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "tmpfs: don't enable large folios if not supported" To: Baolin Wang , , CC: , , , , , , References: Content-Language: en-US From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7B91A18000F X-Stat-Signature: 4469ratns4n8badb1kkooipgjn43fp9w X-Rspam-User: X-HE-Tag: 1776912405-785836 X-HE-Meta: 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 NvaTm5w5 hEBi4ikGLcx6DO1YxfIRQm1qACFx8XwZyp/U6s6lNZv+9Q7u+pLMaKQd3+4Z8xKubB5jQ/cDifbnX+LEMeLTn8UNllYwwAugviFxXxP+jAOpqvEdzyMsUo+GCScmfkiktS0i/6Nx49v/Ud65HdDHBApJcZX5Exw3Vt9WLOrTR/T+MEjYmwHdJ60T7Zskycb4M8S7PDJwcZ5coKWER2Y4OjcNox8a4ValwY6x+kD5m5x0Uomfbd5r+O1OhR92nNHPo6Y6nbpBINRw7RyT2sbiUlJFzUFAYE8lNeIVR/m+28em8El1pxk/EkMk35lsOD7xxl6xUXVzMGAif5Kjce+3kLJwNtTsHMJgfLKsAKCu44G/qd4tCrYBkBNCkkR5tSzsefHHK2ZckKeDbruWrVB+iOjrovA+B5BvdducC Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/2026 9:41 AM, 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/ > Thanks Kefeng for confirming the performance issue. LGTM， Reviewed-by: Kefeng Wang > --- > mm/shmem.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 4ecefe02881d..dafbea53b22d 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3087,10 +3087,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, > cache_no_acl(inode); > if (sbinfo->noswap) > mapping_set_unevictable(inode->i_mapping); > - > - /* Don't consider 'deny' for emergencies and 'force' for testing */ > - if (sbinfo->huge) > - mapping_set_large_folios(inode->i_mapping); > + mapping_set_large_folios(inode->i_mapping); > > switch (mode & S_IFMT) { > default: