From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67DC4157A58 for ; Wed, 24 Apr 2024 06:55:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713941740; cv=none; b=t3iEXU+L0fowCnJ/XA9sDzbyyRaVNO24NjWhKGFMGC4Pmh0gNtievFWfJWiKf2B74JOw05F5OfO6H/sn8iiBHlQCiPeyu3cXshwl7AOAgMRvATms/0UOzt+EBAZVGgDK28evBK8BoXujAhn96XJfGJBWXOT6bCR9QNH4Yaw4/BI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713941740; c=relaxed/simple; bh=TXRX2uyfbwu6I5DEAHexhw0wFLD0sAWld9bXxN+zwSI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u2hWWGc/VBOJC6GoRNUpPBeGYLNzdd4SPFTkAcuD0AFJrP35lTE0BHn1i48C8xi8zUPeUIvH1vTUZ4DCROyvX6y/fdDYFKSwN9eMjJbRAqvETUU2o3V63lh1rk+q+p+V00aWElpliHV5wH5AOeoyC1icNSyvaUY6C2qa1CrZyyg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=ZFNk3/00; arc=none smtp.client-ip=115.124.30.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="ZFNk3/00" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1713941730; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=b07EZ7LT5dczTtPhKaX3n1AzQq/O2KWgxHIqHzYhZFM=; b=ZFNk3/006oB9kJLX2VAIsE52s2taRCMYv8h6MjTchAYAYFL4wxN2MR0/icjOrGGEZZ2IGqIBdr/nxri1jNKlOq6hPwMLgslce9hPkw1UnUyBE3t9BWTFjdkWogfU8CbHxMmZvKE2FxkTiE8PdzHxf5+jcxtMg6u1p+cYGqxxcEQ= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032014016;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0W5BTi-9_1713941726; Received: from 30.97.56.58(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0W5BTi-9_1713941726) by smtp.aliyun-inc.com; Wed, 24 Apr 2024 14:55:28 +0800 Message-ID: Date: Wed, 24 Apr 2024 14:55:26 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/5] add mTHP support for anonymous share pages To: Ryan Roberts , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, david@redhat.com, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ying.huang@intel.com, shy828301@gmail.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <4b998e7d-153f-48cc-a9bb-8c84bb675581@arm.com> From: Baolin Wang In-Reply-To: <4b998e7d-153f-48cc-a9bb-8c84bb675581@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024/4/23 18:41, Ryan Roberts wrote: > On 22/04/2024 08:02, Baolin Wang wrote: >> Anonymous pages have already been supported for multi-size (mTHP) allocation >> through commit 19eaf44954df, that can allow THP to be configured through the >> sysfs interface located at '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'. >> >> However, the anonymous shared pages will ignore the anonymous mTHP rule >> configured through the sysfs interface, and can only use the PMD-mapped >> THP, that is not reasonable. Many implement anonymous page sharing through >> mmap(MAP_SHARED | MAP_ANONYMOUS), especially in database usage scenarios, >> therefore, users expect to apply an unified mTHP strategy for anonymous pages, >> also including the anonymous shared pages, in order to enjoy the benefits of >> mTHP. For example, lower latency than PMD-mapped THP, smaller memory bloat >> than PMD-mapped THP, contiguous PTEs on ARM architecture to reduce TLB miss etc. > > This sounds like a very useful addition! > > Out of interest, can you point me at any workloads (and off-the-shelf benchmarks > for those workloads) that predominantly use shared anon memory? As far as I know, some database related workloads make extensive use of shared anonymous page, such as PolarDB[1] in our Alibaba fleet, or MySQL likely also uses shared anonymous memory. And I still need to do some investigation to measure the performance. [1] https://github.com/ApsaraDB/PolarDB-for-PostgreSQL >> The primary strategy is that, the use of huge pages for anonymous shared pages >> still follows the global control determined by the mount option "huge=" parameter >> or the sysfs interface at '/sys/kernel/mm/transparent_hugepage/shmem_enabled'. >> The utilization of mTHP is allowed only when the global 'huge' switch is enabled. >> Subsequently, the mTHP sysfs interface (/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled) >> is checked to determine the mTHP size that can be used for large folio allocation >> for these anonymous shared pages. > > I'm not sure about this proposed control mechanism; won't it break > compatibility? I could be wrong, but I don't think shmem's use of THP used to > depend upon the value of /sys/kernel/mm/transparent_hugepage/enabled? So it Yes, I realized this after more testing. > doesn't make sense to me that we now depend upon the > /sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled values (which by > default disables all sizes except 2M, which is set to "inherit" from > /sys/kernel/mm/transparent_hugepage/enabled). > > The other problem is that shmem_enabled has a different set of options > (always/never/within_size/advise/deny/force) to enabled (always/madvise/never) > > Perhaps it would be cleaner to do the same trick we did for enabled; Introduce > /mm/transparent_hugepage/hugepage-XXkb/shmem_enabled, which can have all the > same values as the top-level /sys/kernel/mm/transparent_hugepage/shmem_enabled, > plus the additional "inherit" option. By default all sizes will be set to > "never" except 2M, which is set to "inherit". Sounds good to me. But I do not want to copy all same values from top-level '/sys/kernel/mm/transparent_hugepage/shmem_enabled': always within_size advise never deny force For mTHP's shmem_enabled interface, we can just keep below values: always within_size advise never Cause when checking if mTHP can be used for anon shmem, 'deny' is equal to 'never', and 'force' is equal to 'always'. > Of course the huge= mount option would also need to take a per-size option in > this case. e.g. huge=2048kB:advise,64kB:always IMO, I do not want to change the global 'huge=' mount option, which can control both anon shmem and tmpfs, but mTHP now is only applied for anon shmem. So let's keep it be same with the global sysfs interface: /sys/kernel/mm/transparent_hugepage/shmem_enabled. For tmpfs large folio strategy, I plan to address it later, and we may need more discussion to determine if it should follow the file large folio strategy or not (no investigation now). Thanks for reviewing. >> TODO: >> - More testing and provide some performance data. >> - Need more discussion about the large folio allocation strategy for a 'regular >> file' operation created by memfd_create(), for example using ftruncate(fd) to specify >> the 'file' size, which need to follow the anonymous mTHP rule too? >> - Do not split the large folio when share memory swap out. >> - Can swap in a large folio for share memory. >> >> Baolin Wang (5): >> mm: memory: extend finish_fault() to support large folio >> mm: shmem: add an 'order' parameter for shmem_alloc_hugefolio() >> mm: shmem: add THP validation for PMD-mapped THP related statistics >> mm: shmem: add mTHP support for anonymous share pages >> mm: shmem: add anonymous share mTHP counters >> >> include/linux/huge_mm.h | 4 +- >> mm/huge_memory.c | 8 ++- >> mm/memory.c | 25 +++++++--- >> mm/shmem.c | 107 ++++++++++++++++++++++++++++++---------- >> 4 files changed, 108 insertions(+), 36 deletions(-) >>