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 8086A386C08 for ; Mon, 6 Jul 2026 15:19:54 +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=1783351197; cv=none; b=kXewlomVcAbxPUWvmdwhbuusyEaTRxb6zZtadOF4weE1iRdl9vIhxnZSug67THBqF1opopUbKp2U1zs+GNWv6iipcjGsNqAxklY/7ygtK3yXD7QH1FnEk/SyCmmdjTrI47CCJc7lNa6YUnpdyel+6GnwqVqA2ELD14NVljo6Lpg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783351197; c=relaxed/simple; bh=0wWva1iwx4qLX37JXmkOlsNhUVBOzvg6x4IFq0W7BJA=; h=Message-ID:Date:MIME-Version:Subject:From:To:CC:References: In-Reply-To:Content-Type; b=NF7q9nnaQa0hZ2SgetXmm1e9C1Rv2ySzep5wXGQyjoTQTn8GTSGM0ETndWzo7eeDBDoW4MBmdnGcKqmuMpJCYBlOjS8zARvuS77mC9MUUVOlebp1/vagCyaoJIWAoE6NnWdI+xVC7sSSIjLHz6Ct9lZfc/OAHMQMquH8JNv86lQ= 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 4gv6z64pTKzHnH84; Mon, 6 Jul 2026 23:02:26 +0800 (CST) Received: from mscpeml500003.china.huawei.com (unknown [7.188.49.51]) by mail.maildlp.com (Postfix) with ESMTPS id 06F1340574; Mon, 6 Jul 2026 23:03:23 +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; Mon, 6 Jul 2026 18:03:22 +0300 Message-ID: Date: Mon, 6 Jul 2026 18:03:03 +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 From: Gutierrez Asier To: SeongJae Park CC: , , , , , , , , References: <20260617014412.97819-1-sj@kernel.org> <665a31f2-2a42-4caf-be62-8429dc225f42@huawei-partners.com> Content-Language: en-US In-Reply-To: <665a31f2-2a42-4caf-be62-8429dc225f42@huawei-partners.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: mscpeml500003.china.huawei.com (7.188.49.51) To mscpeml500003.china.huawei.com (7.188.49.51) Hi SJ, On 6/20/2026 8:11 PM, 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. >>> # 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. >>> 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? >>> >>> 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. >> >>> >>> 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. >>> >>> 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. > I didn't get a reply to this email. I will update the cover letter and submit a new patch set soon. -- Asier Gutierrez Huawei