From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A8BC078C9A for ; Tue, 23 Apr 2024 10:41:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713868889; cv=none; b=gCEzbtjlGK1JDjwnz3n9SsgWOP9Wct9yuCnyfYx0S8Rh/gMTyJh9QO+4CDaJfqg7JSa8wn5vFeCqPXXaM7OdYGc/Yaj0xHU3/cdT8ph5KjqOBUwKjGS2Cv91bsi7gDsJxov3MS3zaKI0D6dR085oct9hbhJpfaOGffzaxl0o2Ts= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713868889; c=relaxed/simple; bh=3oKcimRYJQ/XdLZiaAT41c0AZ7QVosTbTDGLlxdj5LM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NGJcja6dnSgknqz7WLtQCLoljOEhIDF4OzZiq2P2Eovxi4L8mLKAVgfVsZjZL1k9ZdvPe+Hg4XbnyNJOWyjdzVwasXBS2DrPJaMWmMkIQO+9yM5OJrJcqB3fSuI0/HqJSZLbhYsKRWujDr+vH4btbfhpfOGf/U8LEb/ts5bxWGg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E7D0E339; Tue, 23 Apr 2024 03:41:54 -0700 (PDT) Received: from [10.57.74.127] (unknown [10.57.74.127]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 420F13F7BD; Tue, 23 Apr 2024 03:41:25 -0700 (PDT) Message-ID: <4b998e7d-153f-48cc-a9bb-8c84bb675581@arm.com> Date: Tue, 23 Apr 2024 11:41:23 +0100 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 Content-Language: en-GB To: Baolin Wang , 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: From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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? > > 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 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". 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 > > 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(-) >