From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D10ABC4742C for ; Fri, 13 Nov 2020 11:00:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 23D0722250 for ; Fri, 13 Nov 2020 11:00:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="NnuffV7r" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 23D0722250 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 34F606B00A1; Fri, 13 Nov 2020 06:00:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 28C0A6B00A2; Fri, 13 Nov 2020 06:00:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0B7336B00A3; Fri, 13 Nov 2020 06:00:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0245.hostedemail.com [216.40.44.245]) by kanga.kvack.org (Postfix) with ESMTP id C67916B00A1 for ; Fri, 13 Nov 2020 06:00:50 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6A7FB181AEF0B for ; Fri, 13 Nov 2020 11:00:50 +0000 (UTC) X-FDA: 77479102260.08.egg80_3b0da9e2730e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 4A1821819E769 for ; Fri, 13 Nov 2020 11:00:50 +0000 (UTC) X-HE-Tag: egg80_3b0da9e2730e X-Filterd-Recvd-Size: 14718 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Fri, 13 Nov 2020 11:00:49 +0000 (UTC) Received: by mail-pf1-f176.google.com with SMTP id c66so7344307pfa.4 for ; Fri, 13 Nov 2020 03:00:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=nX63o5by1tYbwNGhtUZNv1hQ/OiXKhkB5Ojf6CHHvwc=; b=NnuffV7r6NSfDuhwf2bhd5zEpczz3fhBtvZwYmO+kvH6qW6/AEJBEBLpU/cCa2QPJR jQPF0kzzSMoHd4iFdNXalgTkLxVVRyDPA/CkNU7K0zoIMFGj7W1pk1tGpb4Ule5pzADo 9BHf+IcWxyZNDeZe82q4GQpdo00DDYQ02dk+O3AjfkbVLD59S2o5NCROSgQ2LiPEUu7h oMDnUJapyyIZYs2XWHW6/LHRXUWdV+fLdRnpSm75T5fB72lgmefWnurvfOq+Vx92Id/B lQNv2ZN7l2HIv2Adete6LF7L5e246fMUPlFtBGldfyHMplIictm0E0LjP12M+GoephDq 6Miw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=nX63o5by1tYbwNGhtUZNv1hQ/OiXKhkB5Ojf6CHHvwc=; b=p3hVCHINA25fvjsSMXLHmYmFadKRMIRp6BLAQ8BHahnNQth/kqZss8GGxzxlo/BMy7 ZJhWoGkSlKG4cv/ryn6j7nhKsZ5e3l8K83B3/X3FkhnVpnw6IYlGmWfKkv1+TNhEP40r TQ40ZVAFnuIibCu3AUpwIhm+OENE0CrzXs/jZDZr0eLrZf40KyppOI4I7GtlOIGgqGYm 9F15vXp9sRoXKzmIBAWaP+NRg9dfuW03eo23V+8TC18Ive9Pw3D0ZrHE9NESPFz9DAGJ b2QunT+cnhgdDo9ew5FUdQ+sCDqI13A4DsKQVezn0MM23WebGeEBDaPCcI4ItXaP4Ssz Zi6Q== X-Gm-Message-State: AOAM533AcApyPfNwr18I5i9QzPz1Cshx7PGro7lVIEGbq5srYxXGj79n ui96lXoKX1irUMliwur1ODfi3Q== X-Google-Smtp-Source: ABdhPJwB5GZnYQE+J8ElKteD7rSellOI6dgOWiUmA81+IFyPh4VtfLKyB5HLNh1C+0Nmy9/fYHwzOA== X-Received: by 2002:a62:7d89:0:b029:18b:86d4:7cbe with SMTP id y131-20020a627d890000b029018b86d47cbemr1690512pfc.77.1605265248256; Fri, 13 Nov 2020 03:00:48 -0800 (PST) Received: from localhost.localdomain ([61.120.150.78]) by smtp.gmail.com with ESMTPSA id f1sm8909959pfc.56.2020.11.13.03.00.36 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 13 Nov 2020 03:00:47 -0800 (PST) From: Muchun Song To: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, osalvador@suse.de, mhocko@suse.com Cc: duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Muchun Song Subject: [PATCH v4 00/21] Free some vmemmap pages of hugetlb page Date: Fri, 13 Nov 2020 18:59:31 +0800 Message-Id: <20201113105952.11638-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi all, This patch series will free some vmemmap pages(struct page structures) associated with each hugetlbpage when preallocated to save memory. Nowadays we track the status of physical page frames using struct page structures arranged in one or more arrays. And here exists one-to-one mapping between the physical page frame and the corresponding struct page structure. The HugeTLB support is built on top of multiple page size support that is provided by most modern architectures. For example, x86 CPUs normally support 4K and 2M (1G if architecturally supported) page sizes. Every HugeTLB has more than one struct page structure. The 2M HugeTLB has 512 struct page structure and 1G HugeTLB has 4096 struct page structures. But in the core of HugeTLB only uses the first 4 (Use of first 4 struct page structures comes from HUGETLB_CGROUP_MIN_ORDER.) struct page structures t= o store metadata associated with each HugeTLB. The rest of the struct page structures are usually read the compound_head field which are all the sam= e value. If we can free some struct page memory to buddy system so that we can save a lot of memory. When the system boot up, every 2M HugeTLB has 512 struct page structures which size is 8 pages(sizeof(struct page) * 512 / PAGE_SIZE). hugetlbpage struct pages(8 pages) page frame= (8 pages) +-----------+ ---virt_to_page---> +-----------+ mapping to +-------= ----+ | | | 0 | -------------> | 0 = | | | | 1 | -------------> | 1 = | | | | 2 | -------------> | 2 = | | | | 3 | -------------> | 3 = | | | | 4 | -------------> | 4 = | | 2M | | 5 | -------------> | 5 = | | | | 6 | -------------> | 6 = | | | | 7 | -------------> | 7 = | | | +-----------+ +-------= ----+ | | | | +-----------+ When a hugetlbpage is preallocated, we can change the mapping from above = to bellow. hugetlbpage struct pages(8 pages) page frame= (8 pages) +-----------+ ---virt_to_page---> +-----------+ mapping to +-------= ----+ | | | 0 | -------------> | 0 = | | | | 1 | -------------> | 1 = | | | | 2 | -------------> +-------= ----+ | | | 3 | -----------------^ ^ ^ = ^ ^ | | | 4 | -------------------+ | = | | | 2M | | 5 | ---------------------+ = | | | | | 6 | -----------------------= + | | | | 7 | -----------------------= --+ | | +-----------+ | | | | +-----------+ For tail pages, the value of compound_head is the same. So we can reuse first page of tail page structs. We map the virtual addresses of the remaining 6 pages of tail page structs to the first tail page struct, and then free these 6 pages. Therefore, we need to reserve at least 2 pages as vmemmap areas. When a hugetlbpage is freed to the buddy system, we should allocate six pages for vmemmap pages and restore the previous mapping relationship. If we uses the 1G hugetlbpage, we can save 4088 pages(There are 4096 page= s for struct page structures, we reserve 2 pages for vmemmap and 8 pages for pa= ge tables. So we can save 4088 pages). This is a very substantial gain. On o= ur server, run some SPDK/QEMU applications which will use 1024GB hugetlbpage= . With this feature enabled, we can save ~16GB(1G hugepage)/~11GB(2MB hugep= age) memory. Because there are vmemmap page tables reconstruction on the freeing/alloc= ating path, it increases some overhead. Here are some overhead analysis. 1) Allocating 10240 2MB hugetlb pages. a) With this patch series applied: # time echo 10240 > /proc/sys/vm/nr_hugepages real 0m0.166s user 0m0.000s sys 0m0.166s # bpftrace -e 'kprobe:alloc_fresh_huge_page { @start[tid] =3D nsecs; }= kretprobe:alloc_fresh_huge_page /@start[tid]/ { @latency =3D hist(nsecs = - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [8K, 16K) 8360 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@= @@@@@@@@| [16K, 32K) 1868 |@@@@@@@@@@@ = | [32K, 64K) 10 | = | [64K, 128K) 2 | = | b) Without this patch series: # time echo 10240 > /proc/sys/vm/nr_hugepages real 0m0.066s user 0m0.000s sys 0m0.066s # bpftrace -e 'kprobe:alloc_fresh_huge_page { @start[tid] =3D nsecs; }= kretprobe:alloc_fresh_huge_page /@start[tid]/ { @latency =3D hist(nsecs = - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [4K, 8K) 10176 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@= @@@@@@@@| [8K, 16K) 62 | = | [16K, 32K) 2 | = | Summarize: this feature is about ~2x slower than before. 2) Freeing 10240 @MB hugetlb pages. a) With this patch series applied: # time echo 0 > /proc/sys/vm/nr_hugepages real 0m0.004s user 0m0.000s sys 0m0.002s # bpftrace -e 'kprobe:__free_hugepage { @start[tid] =3D nsecs; } kretp= robe:__free_hugepage /@start[tid]/ { @latency =3D hist(nsecs - @start[tid= ]); delete(@start[tid]); }' Attaching 2 probes... @latency: [16K, 32K) 10240 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@= @@@@@@@@| b) Without this patch series: # time echo 0 > /proc/sys/vm/nr_hugepages real 0m0.077s user 0m0.001s sys 0m0.075s # bpftrace -e 'kprobe:__free_hugepage { @start[tid] =3D nsecs; } kretp= robe:__free_hugepage /@start[tid]/ { @latency =3D hist(nsecs - @start[tid= ]); delete(@start[tid]); }' Attaching 2 probes... @latency: [4K, 8K) 9950 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@= @@@@@@@@| [8K, 16K) 287 |@ = | [16K, 32K) 3 | = | Summarize: The overhead of __free_hugepage is about ~2-4x slower than = before. But according to the allocation test above, I think that he= re is also ~2x slower than before. But why the 'real' time of patched is smaller than before? = Because In this patch series, the freeing hugetlb is asynchronous(through kwoker). Although the overhead has increased, the overhead is not significant. Lik= e MIke said, "However, remember that the majority of use cases create hugetlb pa= ges at or shortly after boot time and add them to the pool. So, additional overh= ead is at pool creation time. There is no change to 'normal run time' operations= of getting a page from or returning a page to the pool (think page fault/unm= ap)". changelog in v4: 1. Move all the vmemmap functions to hugetlb_vmemmap.c. 2. Make the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP default to y, if we want t= o disable this feature, we should disable it by a boot/kernel command = line. 3. Remove vmemmap_pgtable_{init, deposit, withdraw}() helper functions. 4. Initialize page table lock for vmemmap through core_initcall mechani= sm. Thanks for Mike and Oscar's suggestions. changelog in v3: 1. Rename some helps function name. Thanks Mike. 2. Rework some code. Thanks Mike and Oscar. 3. Remap the tail vmemmap page with PAGE_KERNEL_RO instead of PAGE_KERNEL. Thanks Matthew. 4. Add some overhead analysis in the cover letter. 5. Use vmemap pmd table lock instead of a hugetlb specific global lock. changelog in v2: 1. Fix do not call dissolve_compound_page in alloc_huge_page_vmemmap(). 2. Fix some typo and code style problems. 3. Remove unused handle_vmemmap_fault(). 4. Merge some commits to one commit suggested by Mike. Muchun Song (21): mm/memory_hotplug: Move bootmem info registration API to bootmem_info.c mm/memory_hotplug: Move {get,put}_page_bootmem() to bootmem_info.c mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate mm/hugetlb: Introduce pgtable allocation/freeing helpers mm/bootmem_info: Introduce {free,prepare}_vmemmap_page() mm/bootmem_info: Combine bootmem info and type into page->freelist mm/hugetlb: Initialize page table lock for vmemmap mm/hugetlb: Free the vmemmap pages associated with each hugetlb page mm/hugetlb: Defer freeing of hugetlb pages mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page mm/hugetlb: Introduce remap_huge_page_pmd_vmemmap helper mm/hugetlb: Use PG_slab to indicate split pmd mm/hugetlb: Support freeing vmemmap pages of gigantic page mm/hugetlb: Set the PageHWPoison to the raw error page mm/hugetlb: Flush work when dissolving hugetlb page mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap mm/hugetlb: Merge pte to huge pmd only for gigantic page mm/hugetlb: Gather discrete indexes of tail page mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two Documentation/admin-guide/kernel-parameters.txt | 9 + Documentation/admin-guide/mm/hugetlbpage.rst | 3 + arch/x86/include/asm/hugetlb.h | 17 + arch/x86/include/asm/pgtable_64_types.h | 8 + arch/x86/mm/init_64.c | 7 +- fs/Kconfig | 14 + include/linux/bootmem_info.h | 78 +++ include/linux/hugetlb.h | 19 + include/linux/hugetlb_cgroup.h | 15 +- include/linux/memory_hotplug.h | 27 - mm/Makefile | 2 + mm/bootmem_info.c | 124 ++++ mm/hugetlb.c | 163 +++++- mm/hugetlb_vmemmap.c | 732 ++++++++++++++++++= ++++++ mm/hugetlb_vmemmap.h | 104 ++++ mm/memory_hotplug.c | 116 ---- mm/sparse.c | 5 +- 17 files changed, 1263 insertions(+), 180 deletions(-) create mode 100644 include/linux/bootmem_info.h create mode 100644 mm/bootmem_info.c create mode 100644 mm/hugetlb_vmemmap.c create mode 100644 mm/hugetlb_vmemmap.h --=20 2.11.0