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[23.128.96.18]) by mx.google.com with ESMTP id c3si10019872edw.365.2020.06.22.22.04.26; Mon, 22 Jun 2020 22:05:28 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=H4yUZHte; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728536AbgFWE5o (ORCPT + 99 others); Tue, 23 Jun 2020 00:57:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728155AbgFWE5n (ORCPT ); Tue, 23 Jun 2020 00:57:43 -0400 Received: from mail-ot1-x342.google.com (mail-ot1-x342.google.com [IPv6:2607:f8b0:4864:20::342]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BF47C061573; Mon, 22 Jun 2020 21:57:43 -0700 (PDT) Received: by mail-ot1-x342.google.com with SMTP id u23so15286957otq.10; Mon, 22 Jun 2020 21:57:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=Qk/BBA82A6eXiQM5eC1kOdCcwx9fj/3/eajJARykb7s=; b=H4yUZHteh0VwI+rLFIO8BHLG9QgaOCVIaJKyzHTg9D0eGIfmCxZ7385/EGVyKXbL3N BudHDCEvkjNhoGrsLbf4Q36xQRXYo2ubVWtVf/AiZ/rQ4ZD8abyL1GQof94Xhwy9uOQw faYct2zc8+mwgCvqr5diXfxpj0VuxxienJk/XEqOHK+4waKfyj/IH4wKSdct9kuBZ7+y iShnDa6AkzMYR1ywcFnSqbOywNQrAM2tsx10UJnES4OdviIMsYzDCNOFAE72R1WRaDie jPZbJ89IBDoLm9xxyOFmRGQZMSErcb2iT3OXOz+aH/ccTGihxx8RJ/72hiZzBJMTqNp+ T7Dw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=Qk/BBA82A6eXiQM5eC1kOdCcwx9fj/3/eajJARykb7s=; b=Oat+cIx7mZ5FBxt63PFKRi50JoPPtEu0n7L5Pp9yg6YhM9C8X+L1oAsiZC5ktuwoOA XuDjlypGjzD893QngpIDx88aWuIFhkQN6HLIzJefQ0xsP1xHh30S/BoJNzn6FNcxDEuP l188B9Odjcj9lW4b+ntZ1qRpXF4qcXqcXyYyAG3deiYmi90Mkilrvo9G2LV/QrF3wU9K O/Av8xax9XBdWEaKnarfqsPVLNadSq2Z7E4jzBEwVdF0jfgWzCfX8BpOcdCFhzvUb0yF PfFv02bCuHUlW6N69Pk09HPAh+lMsdG5TlStwJfL/lDIYVVNMvst/gbDLm/MnxvvC49X AtEg== X-Gm-Message-State: AOAM5305JTvP9te1JVjQ7sjr0kmHyPiWqumFwcb4MrxPs/+kHSPsjYs2 MZoNrDygmwD4hcqVe2KUFDg= X-Received: by 2002:a9d:6f81:: with SMTP id h1mr16374346otq.53.1592888262512; Mon, 22 Jun 2020 21:57:42 -0700 (PDT) Received: from ubuntu-n2-xlarge-x86 ([2604:1380:4111:8b00::3]) by smtp.gmail.com with ESMTPSA id n9sm3970152oom.45.2020.06.22.21.57.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2020 21:57:41 -0700 (PDT) Date: Mon, 22 Jun 2020 21:57:40 -0700 From: Nathan Chancellor To: Nitin Gupta Cc: Nitin Gupta , Andrew Morton , Vlastimil Babka , Khalid Aziz , Oleksandr Natalenko , Michal Hocko , Mel Gorman , Matthew Wilcox , Mike Kravetz , Joonsoo Kim , David Rientjes , linux-kernel , linux-mm , Linux API , linux-mips@vger.kernel.org Subject: Re: [PATCH v8] mm: Proactive compaction Message-ID: <20200623045740.GA2912137@ubuntu-n2-xlarge-x86> References: <20200616204527.19185-1-nigupta@nvidia.com> <20200623022636.GA1051134@ubuntu-n2-xlarge-x86> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 22, 2020 at 09:32:12PM -0700, Nitin Gupta wrote: > On 6/22/20 7:26 PM, Nathan Chancellor wrote: > > On Tue, Jun 16, 2020 at 01:45:27PM -0700, Nitin Gupta wrote: > >> For some applications, we need to allocate almost all memory as > >> hugepages. However, on a running system, higher-order allocations can > >> fail if the memory is fragmented. Linux kernel currently does on-demand > >> compaction as we request more hugepages, but this style of compaction > >> incurs very high latency. Experiments with one-time full memory > >> compaction (followed by hugepage allocations) show that kernel is able > >> to restore a highly fragmented memory state to a fairly compacted memory > >> state within <1 sec for a 32G system. Such data suggests that a more > >> proactive compaction can help us allocate a large fraction of memory as > >> hugepages keeping allocation latencies low. > >> > >> For a more proactive compaction, the approach taken here is to define a > >> new sysctl called 'vm.compaction_proactiveness' which dictates bounds > >> for external fragmentation which kcompactd tries to maintain. > >> > >> The tunable takes a value in range [0, 100], with a default of 20. > >> > >> Note that a previous version of this patch [1] was found to introduce > >> too many tunables (per-order extfrag{low, high}), but this one reduces > >> them to just one sysctl. Also, the new tunable is an opaque value > >> instead of asking for specific bounds of "external fragmentation", which > >> would have been difficult to estimate. The internal interpretation of > >> this opaque value allows for future fine-tuning. > >> > >> Currently, we use a simple translation from this tunable to [low, high] > >> "fragmentation score" thresholds (low=100-proactiveness, high=low+10%). > >> The score for a node is defined as weighted mean of per-zone external > >> fragmentation. A zone's present_pages determines its weight. > >> > >> To periodically check per-node score, we reuse per-node kcompactd > >> threads, which are woken up every 500 milliseconds to check the same. If > >> a node's score exceeds its high threshold (as derived from user-provided > >> proactiveness value), proactive compaction is started until its score > >> reaches its low threshold value. By default, proactiveness is set to 20, > >> which implies threshold values of low=80 and high=90. > >> > >> This patch is largely based on ideas from Michal Hocko [2]. See also the > >> LWN article [3]. > >> > >> Performance data > >> ================ > >> > >> System: x64_64, 1T RAM, 80 CPU threads. > >> Kernel: 5.6.0-rc3 + this patch > >> > >> echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/enabled > >> echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/defrag > >> > >> Before starting the driver, the system was fragmented from a userspace > >> program that allocates all memory and then for each 2M aligned section, > >> frees 3/4 of base pages using munmap. The workload is mainly anonymous > >> userspace pages, which are easy to move around. I intentionally avoided > >> unmovable pages in this test to see how much latency we incur when > >> hugepage allocations hit direct compaction. > >> > >> 1. Kernel hugepage allocation latencies > >> > >> With the system in such a fragmented state, a kernel driver then > >> allocates as many hugepages as possible and measures allocation > >> latency: > >> > >> (all latency values are in microseconds) > >> > >> - With vanilla 5.6.0-rc3 > >> > >> percentile latency > >> –––––––––– ––––––– > >> 5 7894 > >> 10 9496 > >> 25 12561 > >> 30 15295 > >> 40 18244 > >> 50 21229 > >> 60 27556 > >> 75 30147 > >> 80 31047 > >> 90 32859 > >> 95 33799 > >> > >> Total 2M hugepages allocated = 383859 (749G worth of hugepages out of > >> 762G total free => 98% of free memory could be allocated as hugepages) > >> > >> - With 5.6.0-rc3 + this patch, with proactiveness=20 > >> > >> sysctl -w vm.compaction_proactiveness=20 > >> > >> percentile latency > >> –––––––––– ––––––– > >> 5 2 > >> 10 2 > >> 25 3 > >> 30 3 > >> 40 3 > >> 50 4 > >> 60 4 > >> 75 4 > >> 80 4 > >> 90 5 > >> 95 429 > >> > >> Total 2M hugepages allocated = 384105 (750G worth of hugepages out of > >> 762G total free => 98% of free memory could be allocated as hugepages) > >> > >> 2. JAVA heap allocation > >> > >> In this test, we first fragment memory using the same method as for (1). > >> > >> Then, we start a Java process with a heap size set to 700G and request > >> the heap to be allocated with THP hugepages. We also set THP to madvise > >> to allow hugepage backing of this heap. > >> > >> /usr/bin/time > >> java -Xms700G -Xmx700G -XX:+UseTransparentHugePages -XX:+AlwaysPreTouch > >> > >> The above command allocates 700G of Java heap using hugepages. > >> > >> - With vanilla 5.6.0-rc3 > >> > >> 17.39user 1666.48system 27:37.89elapsed > >> > >> - With 5.6.0-rc3 + this patch, with proactiveness=20 > >> > >> 8.35user 194.58system 3:19.62elapsed > >> > >> Elapsed time remains around 3:15, as proactiveness is further increased. > >> > >> Note that proactive compaction happens throughout the runtime of these > >> workloads. The situation of one-time compaction, sufficient to supply > >> hugepages for following allocation stream, can probably happen for more > >> extreme proactiveness values, like 80 or 90. > >> > >> In the above Java workload, proactiveness is set to 20. The test starts > >> with a node's score of 80 or higher, depending on the delay between the > >> fragmentation step and starting the benchmark, which gives more-or-less > >> time for the initial round of compaction. As t he benchmark consumes > >> hugepages, node's score quickly rises above the high threshold (90) and > >> proactive compaction starts again, which brings down the score to the > >> low threshold level (80). Repeat. > >> > >> bpftrace also confirms proactive compaction running 20+ times during the > >> runtime of this Java benchmark. kcompactd threads consume 100% of one of > >> the CPUs while it tries to bring a node's score within thresholds. > >> > >> Backoff behavior > >> ================ > >> > >> Above workloads produce a memory state which is easy to compact. > >> However, if memory is filled with unmovable pages, proactive compaction > >> should essentially back off. To test this aspect: > >> > >> - Created a kernel driver that allocates almost all memory as hugepages > >> followed by freeing first 3/4 of each hugepage. > >> - Set proactiveness=40 > >> - Note that proactive_compact_node() is deferred maximum number of times > >> with HPAGE_FRAG_CHECK_INTERVAL_MSEC of wait between each check > >> (=> ~30 seconds between retries). > >> > >> [1] https://patchwork.kernel.org/patch/11098289/ > >> [2] https://lore.kernel.org/linux-mm/20161230131412.GI13301@dhcp22.suse.cz/ > >> [3] https://lwn.net/Articles/817905/ > >> > >> Signed-off-by: Nitin Gupta > >> Reviewed-by: Vlastimil Babka > >> Reviewed-by: Khalid Aziz > >> Reviewed-by: Oleksandr Natalenko > >> Tested-by: Oleksandr Natalenko > >> To: Andrew Morton > >> CC: Vlastimil Babka > >> CC: Khalid Aziz > >> CC: Michal Hocko > >> CC: Mel Gorman > >> CC: Matthew Wilcox > >> CC: Mike Kravetz > >> CC: Joonsoo Kim > >> CC: David Rientjes > >> CC: Nitin Gupta > >> CC: Oleksandr Natalenko > >> CC: linux-kernel > >> CC: linux-mm > >> CC: Linux API > > > > This is now in -next and causes the following build failure: > > > > $ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mipsel-linux- O=out/mipsel distclean malta_kvm_guest_defconfig mm/compaction.o > > In file included from include/linux/dev_printk.h:14, > > from include/linux/device.h:15, > > from include/linux/node.h:18, > > from include/linux/cpu.h:17, > > from mm/compaction.c:11: > > In function 'fragmentation_score_zone', > > inlined from '__compact_finished' at mm/compaction.c:1982:11, > > inlined from 'compact_zone' at mm/compaction.c:2062:8: > > include/linux/compiler.h:339:38: error: call to '__compiletime_assert_301' declared with attribute error: BUILD_BUG failed > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^ > > include/linux/compiler.h:320:4: note: in definition of macro '__compiletime_assert' > > 320 | prefix ## suffix(); \ > > | ^~~~~~ > > include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^~~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > > | ^~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG' > > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > > | ^~~~~~~~~~~~~~~~ > > arch/mips/include/asm/page.h:70:30: note: in expansion of macro 'BUILD_BUG' > > 70 | #define HUGETLB_PAGE_ORDER ({BUILD_BUG(); 0; }) > > | ^~~~~~~~~ > > mm/compaction.c:66:32: note: in expansion of macro 'HUGETLB_PAGE_ORDER' > > 66 | #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER > > | ^~~~~~~~~~~~~~~~~~ > > mm/compaction.c:1898:28: note: in expansion of macro 'COMPACTION_HPAGE_ORDER' > > 1898 | extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); > > | ^~~~~~~~~~~~~~~~~~~~~~ > > In function 'fragmentation_score_zone', > > inlined from 'kcompactd' at mm/compaction.c:1918:12: > > include/linux/compiler.h:339:38: error: call to '__compiletime_assert_301' declared with attribute error: BUILD_BUG failed > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^ > > include/linux/compiler.h:320:4: note: in definition of macro '__compiletime_assert' > > 320 | prefix ## suffix(); \ > > | ^~~~~~ > > include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^~~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > > | ^~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG' > > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > > | ^~~~~~~~~~~~~~~~ > > arch/mips/include/asm/page.h:70:30: note: in expansion of macro 'BUILD_BUG' > > 70 | #define HUGETLB_PAGE_ORDER ({BUILD_BUG(); 0; }) > > | ^~~~~~~~~ > > mm/compaction.c:66:32: note: in expansion of macro 'HUGETLB_PAGE_ORDER' > > 66 | #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER > > | ^~~~~~~~~~~~~~~~~~ > > mm/compaction.c:1898:28: note: in expansion of macro 'COMPACTION_HPAGE_ORDER' > > 1898 | extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); > > | ^~~~~~~~~~~~~~~~~~~~~~ > > In function 'fragmentation_score_zone', > > inlined from 'kcompactd' at mm/compaction.c:1918:12: > > include/linux/compiler.h:339:38: error: call to '__compiletime_assert_301' declared with attribute error: BUILD_BUG failed > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^ > > include/linux/compiler.h:320:4: note: in definition of macro '__compiletime_assert' > > 320 | prefix ## suffix(); \ > > | ^~~~~~ > > include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^~~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > > | ^~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG' > > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > > | ^~~~~~~~~~~~~~~~ > > arch/mips/include/asm/page.h:70:30: note: in expansion of macro 'BUILD_BUG' > > 70 | #define HUGETLB_PAGE_ORDER ({BUILD_BUG(); 0; }) > > | ^~~~~~~~~ > > mm/compaction.c:66:32: note: in expansion of macro 'HUGETLB_PAGE_ORDER' > > 66 | #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER > > | ^~~~~~~~~~~~~~~~~~ > > mm/compaction.c:1898:28: note: in expansion of macro 'COMPACTION_HPAGE_ORDER' > > 1898 | extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); > > | ^~~~~~~~~~~~~~~~~~~~~~ > > In function 'fragmentation_score_zone', > > inlined from 'kcompactd' at mm/compaction.c:1918:12: > > include/linux/compiler.h:339:38: error: call to '__compiletime_assert_301' declared with attribute error: BUILD_BUG failed > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^ > > include/linux/compiler.h:320:4: note: in definition of macro '__compiletime_assert' > > 320 | prefix ## suffix(); \ > > | ^~~~~~ > > include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' > > 339 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > | ^~~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > > | ^~~~~~~~~~~~~~~~~~ > > include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG' > > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > > | ^~~~~~~~~~~~~~~~ > > arch/mips/include/asm/page.h:70:30: note: in expansion of macro 'BUILD_BUG' > > 70 | #define HUGETLB_PAGE_ORDER ({BUILD_BUG(); 0; }) > > | ^~~~~~~~~ > > mm/compaction.c:66:32: note: in expansion of macro 'HUGETLB_PAGE_ORDER' > > 66 | #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER > > | ^~~~~~~~~~~~~~~~~~ > > mm/compaction.c:1898:28: note: in expansion of macro 'COMPACTION_HPAGE_ORDER' > > 1898 | extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); > > | ^~~~~~~~~~~~~~~~~~~~~~ > > make[3]: *** [scripts/Makefile.build:281: mm/compaction.o] Error 1 > > make[3]: Target '__build' not remade because of errors. > > make[2]: *** [Makefile:1765: mm] Error 2 > > make[2]: Target 'mm/compaction.o' not remade because of errors. > > make[1]: *** [Makefile:336: __build_one_by_one] Error 2 > > make[1]: Target 'distclean' not remade because of errors. > > make[1]: Target 'malta_kvm_guest_defconfig' not remade because of errors. > > make[1]: Target 'mm/compaction.o' not remade because of errors. > > make: *** [Makefile:185: __sub-make] Error 2 > > make: Target 'distclean' not remade because of errors. > > make: Target 'malta_kvm_guest_defconfig' not remade because of errors. > > make: Target 'mm/compaction.o' not remade because of errors. > > > > I am not sure why MIPS is special with its handling of hugepage support > > but I am far from a MIPS expert :) > > > > Can you check if this patch fixes the compile error: > > > diff --git a/mm/compaction.c b/mm/compaction.c > index 45fd24a0ea0b..02963ffb9e70 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -62,7 +62,7 @@ static const unsigned int > HPAGE_FRAG_CHECK_INTERVAL_MSEC = 500; > */ > #if defined CONFIG_TRANSPARENT_HUGEPAGE > #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER > -#elif defined HUGETLB_PAGE_ORDER > +#elif defined CONFIG_HUGETLBFS > #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER > #else > #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT) > > > > Tested-by: Nathan Chancellor # build