From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (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 1E1B341C303 for ; Tue, 7 Jul 2026 13:31:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783431078; cv=none; b=LcfSSZM6U+V+oesqZ0EW8GZvsntkGXGNcUu5EfXlE+xiaaHIWtfvQe1p8Dxp3g8b89ZFDrcy1iZU3C2izxjXMW8ofp2v3vI3Q8J5unG2ffq2u0XF6aSo9wyn7FEz6LDFY1BVwjBtaGi3LJzk1WzT9c8JDDjg8pinHTxn5+cvyoU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783431078; c=relaxed/simple; bh=U4oiQlHDziQlc0zQVYFqNs3mydE2hP2DnIuob8C/gQk=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=kVExj91SCX+eE/o+qzXhcQlVMvm9vvsRexuG0+IeTU2iqLmLbnlNw5wg1ghKl0dw52PIVKdrSJ0rfR3MitVjp9cu/PKd/CmSFBY+Co8j+minUK841I9IDWfUqx3pn56sHoEDEIMxGy4kjVbKIbuZaka5mggVNjzbSLAFBN/CUd8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei-partners.com; spf=pass smtp.mailfrom=huawei-partners.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei-partners.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei-partners.com Received: from mail.maildlp.com (unknown [172.18.224.150]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4gvhtG19cnzHnH51; Tue, 7 Jul 2026 21:30:14 +0800 (CST) Received: from mscpeml500003.china.huawei.com (unknown [7.188.49.51]) by mail.maildlp.com (Postfix) with ESMTPS id 5C7B840574; Tue, 7 Jul 2026 21:31:12 +0800 (CST) Received: from [10.123.123.154] (10.123.123.154) by mscpeml500003.china.huawei.com (7.188.49.51) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 7 Jul 2026 16:31:11 +0300 Message-ID: <9e29abd7-e6d8-4bb0-95f8-1dc3089ca2ce@huawei-partners.com> Date: Tue, 7 Jul 2026 16:31:03 +0300 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: [PATCH v1 0/3] mm/damon: Introduce a huge page collapsing mechanism using auto tuning To: SeongJae Park CC: , , , , , , , , References: <20260620200254.82414-1-sj@kernel.org> Content-Language: en-US From: Gutierrez Asier In-Reply-To: <20260620200254.82414-1-sj@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: mscpeml500004.china.huawei.com (7.188.26.250) To mscpeml500003.china.huawei.com (7.188.49.51) On 6/20/2026 11:02 PM, SeongJae Park wrote: > On Sat, 20 Jun 2026 20:11:46 +0300 Gutierrez Asier wrote: > >> Hi SJ, >> >> So sorry, I missed your email. I just found it. Sorry for the late answer. >> >> On 6/17/2026 4:44 AM, SeongJae Park wrote: >>> On Tue, 16 Jun 2026 15:03:13 +0000 wrote: >>> >>>> From: Asier Gutierrez >>>> >>>> Overview >>>> ======== >>>> >>>> This patch set introduces a new autotuning which allows to collapse >>>> hot regions into hugepages. >>>> >>>> Motivation >>>> ========== >>>> >>>> Since TLB is a bottleneck for many systems[1], a way to optimize TLB >>>> misses (or hits) is to use huge pages. Unfortunately, using "always" >>>> in THP leads to memory fragmentation and memory waste. For this reason, >>>> most application guides and system administrators suggest to disable THP. >>>> >>>> Currently DAMON has DAMOS_HUGEPAGE, DAMOS_NONHUGEPAGE and DAMOS_COLLAPSE. >>>> However, there is no way to tune the settings. It will collapse all the >>>> hot regions that meet the access pattern. If the server is a bare metal >>>> database or big data server, this will also lead to eventual fragmentation. >>>> >>>> Additionally, currently THP is set globally. Ideally, there should be a >>>> way to control which tasks can use huge pages. >>> >>> Could you please reword for prctl(PR_SET_THP_DISABLE) like per-process control >>> cases, as we discussed [1] on RFC v3? >>> >>>> >>>> Solution >>>> ======== >>>> >>>> DAMON has now a way to autotune some of the variables and adjust quotas >>>> automatically, so that DAMON is fired only under the right circumstances. >>>> It would be nice to have something similar, but for huge pages. >>>> >>>> A new autotuning quota goal[2], damos_hugepage_mem_bp, is introduced, >>>> which checks the huge page consumption to total memory consumption. This >>>> new quota mechanism reuses current autotuning architecture. >>>> >>>> A new sample module (SAMPLE_DAMON_HPAGE) is introduced to demonstrate >>>> the use of huge pages collapse autotuning. The goal is to collapse hot >>>> regions of a given process into huge pages. The sample module launches >>>> a kdamond thread for a certain task provided by the user through >>>> taget_pid module argument. Hugepage goal autotuning will automatically >>>> adjust the aggressiveness of hot region collapses. >>>> >>>> This sample module also has a user autotuning knob which allows the >>>> user to adjust the aggressiveness of page collapsing. >>>> >>>> Benchmarks >>>> ========== >>>> >>>> Huge page collapse autotuning was tested in a physicial machine with >>>> MariaDB 10.5.29 and sysbench as the benchmark framework. >>>> >>>> The hugepage module was set up in the following way: >>>> >>>> # echo 1000 > min_age >>>> # echo 1000 > quota_percentage_hugepage >>> >>> I guess this is the quota goal? What is the unit? I guess it is aparently not >>> percentage? The name doesn't sound like very consistent or intuitive. How >>> about hugepage_mem_bp or target_hugepage_mem_bp? >> Right, we agreed to change the name. I will correct it. > > Thank you. Because we agreed to drop the module, this could simply be dropped? > >>>> # echo $(pidof mariadbd) > taget_pid >>>> # echo on > enabled >>>> >>>> The goal was to achieve 5% of the total memory used as hugepage. >>> >>> I guess this is what the above example is setting using >>> 'quotta_percentage_hugepage'? If so, it means the unit is 1/20000 ? Is this >>> correct...? >> I actually set it to 500. I will update the cover letter. > > I think changes of this series is matured and very close to land. > Discrepancies in the cover letter and commit messages are my concern that > blocking this series. Please keep everything up to date and in high quality, > from the next version. I will test it with a bigger database. >>>> Since the database was not very big, we may not be able to achieve >>>> high amount of huge pages per total memory consumption ratio. >>> >>> I believe this patch series will work as you explained. But, it seems bit >>> weird to show a test result that doesn't demonstrate what this patch is aimed >>> to achive. Could you increase the size of the database? IIRC, you were able >>> to show the percentage is over-achived case in an early version. >> Actually, this is what I got using the TEMPORAL quota goals. With the regular >> quota goals, it actually over-achieves the goal. >> >> Is this an actual bug in the TEMPORAL quota goal? > > You mentioned "Since the database was not very big, we may not be able to ...". > Based on that, I was assuming you will be able to make the goal achieved, by > increasing the database size. Now you are saying about the goal. > > Do you mean the database size is not expected to contributed to this result? > > Of course TEMPORAL goal might have bugs. I find no clue from this datta, > though. Do you have some evidences that make you suspect it? If so, could you > please share? > >>>> >>>> The table below shows the memory consumption over time. Timestamp is in >>>> second and the memory usage in is MBytes. Gaps in the timestamp means >>>> that no changes in the hugepage consumption happened over that period >>>> of time in MB. The total used memory is calculated as >>>> mem_total - mem free. The huge page used is calculated as >>>> huge_page_anon + huge_page_shmem + huge_page_file. The table also >>>> shows the huge pages to total memory ratio. >>>> >>>> Hugepage autotune benchmark: >>>> +-----------+----------------+----------------+----------------------+ >>>> | timestamp | total mem used | huge page used | percentage hugepage | >>>> +-----------+----------------+----------------+----------------------+ >>>> | 0 | 3044.988281 | 0 | 0% | >>>> | 22 | 3160.207031 | 2 | 0.06% | >>>> | 30 | 3250.90625 | 4 | 0.12% | >>>> | 69 | 3781.238281 | 6 | 0.16% | >>>> | 71 | 3822.226563 | 8 | 0.21% | >>>> | 72 | 3846.578125 | 10 | 0.26% | >>>> | 73 | 3852.402344 | 12 | 0.31% | >>>> | 74 | 3868 | 14 | 0.36% | >>>> | 75 | 3881.84375 | 104 | 2.68% | >>>> | 275 | 4194.175781 | 106 | 2.52% | >>>> +-----------+----------------+----------------+----------------------+ >>>> After second 275, no more pages are collapsed into hugepages >>>> >>>> >>>> THP (always) benchmark: >>>> +-----------+----------------+----------------+---------------------+ >>>> | timestamp | total mem used | huge page used | percentage hugepage | >>>> +-----------+----------------+----------------+---------------------+ >>>> | 1 | 4489.320313 | 184 | 4.098615986 | >>>> | 15 | 4581.871094 | 214 | 4.670580984 | >>>> | 30 | 4757.742188 | 376 | 7.902908253 | >>>> | 45 | 4937.574219 | 558 | 11.30109595 | >>>> | 60 | 5147.867188 | 728 | 14.14177898 | >>>> | 75 | 5407.0625 | 918 | 16.97779524 | >>>> | 95 | 5668.796875 | 1040 | 18.34604455 | >>>> | 105 | 5723.839844 | 1056 | 18.44915352 | >>>> | 115 | 5736.84375 | 1072 | 18.68623317 | >>>> | 125 | 5732.042969 | 1088 | 18.98101612 | >>>> | 186 | 5753.601563 | 1184 | 20.57841488 | >>>> | 246 | 5746.398438 | 1280 | 22.27482159 | >>>> | 306 | 5752.128906 | 1376 | 23.92157795 | >>>> | 367 | 5772.5625 | 1472 | 25.49994045 | >>>> | 427 | 5832.019531 | 1568 | 26.88605536 | >>>> | 488 | 5813.246094 | 1664 | 28.62428277 | >>>> | 548 | 5807.621094 | 1760 | 30.30500736 | >>>> | 598 | 5841.253906 | 1822 | 31.19193292 | >>>> | 669 | 5982.160156 | 1854 | 30.99214918 | >>>> | 931 | 5946.605469 | 1868 | 31.41287933 | >>>> | 981 | 6020.207031 | 1896 | 31.49393352 | >>>> | 991 | 5988.445313 | 1910 | 31.89475566 | >>>> | 1011 | 5988.570313 | 1926 | 32.16126554 | >>>> | 1032 | 6016.039063 | 1936 | 32.18064211 | >>>> | 1575 | 6057.289063 | 1968 | 32.48978181 | >>>> | 1606 | 6026.167969 | 2000 | 33.18858702 | >>>> +-----------+----------------+----------------+---------------------+ >>>> I ignored some points to make the table shorter. Anyway, the amount >>>> of memory consumption, total and huge pages, is a lot higher than >>>> with DAMON hugepage autotuning. >>> >>> Could you further clarify why it is, and what this means >> Memory fragmentation. I will add information about memory fragmentation >> in the next cover letter. >> > > Yes, please. Let's make the complete story of the benchmark. > >>>> >>>> Performance: >>>> Baseline (no THP, module off) -> 18,162.45 transactions per second >>>> Hugepage autotune -> 18,211.82 transactions per second (+0.27% improvement) >>>> THP always -> 18,388.3 (+1.24%) >>>> THP madvise -> 18,179.25 (+0.09%) >>>> >>>> Improvement is due to lower TLB misses >>> >>> So this result says THP always is much better than the Hugepage autotune in >>> terms of the performance. Maybe you want to claim Hugepage autotune is better >>> in terms of the memory efficiency? Could you please clarify further? >> It's better than THP "never", but worse than THP "always". THP "always" is worse >> in terms of memory consumption, "always" is worse. > > I think it is arguable, but yes, please make the argument clear. We can > discuss only after that. > > Since we agreed to drop the module, you may need to do the benchmark again, > using DAMON sysfs interface of 'damo'. I'd encourage 'damo' path. Extending > it for ddamos_quota_hugepage_mem_bp should be easy. Let me know if you need my > help. > > Because the change is simple, I wouldn't request you to show clear performance > benefit. But I want it to clearly show the functionality. That is, by > applying the new feature, we should be able to show the hugepage memory ratio > is controllable. I agree. I will start testing manually through sysfs first. Once it works, I will fork damo, make small changes to support the functionality and provide all the details in the cover letter using damo. >>>> >>>> Patches Sequence >>>> ================ >>>> Patch 1 -> Introduce DAMOS_QUOTA_HUGEPAGE_MEM_BP and autotuning >>>> Patch 2 -> Module that demonstrates how to use >>>> DAMOS_QUOTA_HUGEPAGE_MEM_BP and DAMOS_QUOTA_GOAL_TUNER_TEMPORAL >>>> Patch 3 -> Support for DAMOS_QUOTA_HUGEPAGE_MEM_BP in sysfs-schemes >>>> >>>> Changes from previous versions >>>> ============================== >>>> RFC 4[3] -> v1 >>>> - Renamed config to SAMPLE_DAMON_HPAGE, file to hpage.c and >>>> functions to damon_sample_hpage_... >>>> - Make the module depend on TRANSPARENT_HUGEPAGE, since >>>> the module will need some THP functions anyway >>>> - Removed documentation, since this is just a sample module >>>> - Removed DAMOS_QUOTA_HUGEPAGE_MEM_BP from >>>> damos_sysfs_add_quota_score >>>> - Added a short description of the module in Kconfig >>> >>> Thank you for continuing this work! >>> >>> [...] >>> >>>> [1] https://dl.acm.org/doi/pdf/10.1145/3307650.3322227 >>>> [2] https://lore.kernel.org/e67f05ad-dbb9-45e6-ba30-b167a99ac67d@huawei-partners.com >>>> [3] https://lore.kernel.org/20260611150244.3454699-1-gutierrez.asier@huawei-partners.com >>>> [4] https://lore.kernel.org/20260604150338.501128-1-gutierrez.asier@huawei-partners.com >>>> [5] https://lore.kernel.org/20260522145518.158910-1-gutierrez.asier@huawei-partners.com >>>> [6] https://lore.kernel.org/20260522171210.900B11F00A3D@smtp.kernel.org >>>> [7] https://lore.kernel.org/20260522171633.AAF5B1F000E9@smtp.kernel.org >>>> [8] https://lore.kernel.org/20260430134139.2446417-1-gutierrez.asier@huawei-partners.com >>>> [9] https://lore.kernel.org/all/20260430154338.E22E6C2BCB3@smtp.kernel.org/ >>> >>> [1] https://lore.kernel.org/9f9e2159-5a6b-496f-9633-fa06c0217948@huawei-partners.com >>> >>> >>> Thanks, >>> SJ >>> >>> [...] >>> >> >> SJ, once again, sorry for the late answer. Please, disregard my new patch set, I will fix >> it with your feedback. > > No worries. Thank you for your grateful continued work on this. > > > Thanks, > SJ > > [...] > -- Asier Gutierrez Huawei