From patchwork Thu Apr 15 08:39:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 12204659 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=-11.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 E8CBCC433ED for ; Thu, 15 Apr 2021 08:42:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C180F611CD for ; Thu, 15 Apr 2021 08:42:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231766AbhDOImq (ORCPT ); Thu, 15 Apr 2021 04:42:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231774AbhDOImp (ORCPT ); Thu, 15 Apr 2021 04:42:45 -0400 Received: from mail-pf1-x42c.google.com (mail-pf1-x42c.google.com [IPv6:2607:f8b0:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1D43C061756 for ; Thu, 15 Apr 2021 01:42:16 -0700 (PDT) Received: by mail-pf1-x42c.google.com with SMTP id o123so15602741pfb.4 for ; Thu, 15 Apr 2021 01:42:16 -0700 (PDT) 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=ztU2Acg0dMiojA7f/XnfsJKLkpkhNQKf4xT+eFnEllA=; b=NZ8qQc3GnlQ5E8gK5iIN3Cf8y2N2tfQqyIOit/7RtYXSQKXGsVmzPba24eDrwmlfFX h2ibyDEE2Lcp5HkFF4lUg/l3pgSo/iypxDQIH5bVsR3SzpH3ES4jIGO05DihtMpsqsxj aIy/aFfP0AfRLl0HpA2kO6lCaPVYBsJTDTvgXBEobiJCZQ86cuZyOKfpzUk72rqq2Asc VvWfNhEjgIdeddNIeBdXWNP3AvNRiUd6VljX9Wyd9Sgj+jw8fa3/C6MPGT3VXfYdKPgT 8oRp1vJT8Jp9rRpW2DFRmUhZmTdKds4goPNJHov4tMlGMpKAkRCGWFdA2qz1S+HG9EG8 isbA== 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=ztU2Acg0dMiojA7f/XnfsJKLkpkhNQKf4xT+eFnEllA=; b=uJfgJFFv6OCOOzzzGEKXgaTm3o9gRopuJu3VyeR792bNBKxIKY6vYGVdB/reWCMxNy 17VzNbZPBnvXPs9EdnK2d+al73GUySWI5mQEFhQK1nmN0vObHnvuuXSJJjNbHfm7FZBg 7rOahOOXBKgtzNA6SDg3KNKEFK2XaBLGPJIQTlnkRsD2Z6tufoYaPWMTaa7oJZIVPDwl klwMPVvyPMRQJs7QPxhvRR4K0ky2NzDFm+f5JLS8dJXjpYeuT3iLso+HzePv3JpWCYD8 2rYVs0cOVeuvIsxGxJftoHwTJTFcst0BMH7fIZ6CSug2DUDXjNarP+Pct7hH5esnqQyq 6LzA== X-Gm-Message-State: AOAM532rL+9Uz3JZdvvwDMmN9G4dlGUEHIo15bcSes+Qbg5zvdMrQ8+2 EQNdeTsDTvanBH6O+puZKn7CLA== X-Google-Smtp-Source: ABdhPJyc4rkJPMXDUn7IRSP8a0BOjXPGa1ixI/MWVdO14zODslWGxtghZCrEXkEU4JJ+Pye/xj9DEw== X-Received: by 2002:a65:4481:: with SMTP id l1mr2471083pgq.42.1618476136125; Thu, 15 Apr 2021 01:42:16 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.234]) by smtp.gmail.com with ESMTPSA id e13sm1392365pgt.91.2021.04.15.01.42.05 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Apr 2021 01:42:15 -0700 (PDT) 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, 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, song.bao.hua@hisilicon.com, david@redhat.com, naoya.horiguchi@nec.com, joao.m.martins@oracle.com Cc: duanxiongchun@bytedance.com, fam.zheng@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 v20 0/9] Free some vmemmap pages of HugeTLB page Date: Thu, 15 Apr 2021 16:39:56 +0800 Message-Id: <20210415084005.25049-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hi, Since Mike's patches (make hugetlb put_page safe for all calling contexts[1]) applied into the next-20210412. We can move forward on this patch series now. This patch series will free some vmemmap pages(struct page structures) associated with each HugeTLB page when preallocated to save memory. In order to reduce the difficulty of the first version of code review. From this version, we disable PMD/huge page mapping of vmemmap if this feature was enabled. This acutely eliminates a bunch of the complex code doing page table manipulation. When this patch series is solid, we cam add the code of vmemmap page table manipulation in the future. The struct page structures (page structs) are used to describe a physical page frame. By default, there is an one-to-one mapping from a page frame to it's corresponding page struct. The HugeTLB pages consist of multiple base page size pages and is supported by many architectures. See hugetlbpage.rst in the Documentation directory for more details. On the x86 architecture, HugeTLB pages of size 2MB and 1GB are currently supported. Since the base page size on x86 is 4KB, a 2MB HugeTLB page consists of 512 base pages and a 1GB HugeTLB page consists of 4096 base pages. For each base page, there is a corresponding page struct. Within the HugeTLB subsystem, only the first 4 page structs are used to contain unique information about a HugeTLB page. HUGETLB_CGROUP_MIN_ORDER provides this upper limit. The only 'useful' information in the remaining page structs is the compound_head field, and this field is the same for all tail pages. By removing redundant page structs for HugeTLB pages, memory can returned to the buddy allocator for other uses. When the system boot up, every 2M HugeTLB has 512 struct page structs which size is 8 pages(sizeof(struct page) * 512 / PAGE_SIZE). HugeTLB struct pages(8 pages) page frame(8 pages) +-----------+ ---virt_to_page---> +-----------+ mapping to +-----------+ | | | 0 | -------------> | 0 | | | +-----------+ +-----------+ | | | 1 | -------------> | 1 | | | +-----------+ +-----------+ | | | 2 | -------------> | 2 | | | +-----------+ +-----------+ | | | 3 | -------------> | 3 | | | +-----------+ +-----------+ | | | 4 | -------------> | 4 | | 2MB | +-----------+ +-----------+ | | | 5 | -------------> | 5 | | | +-----------+ +-----------+ | | | 6 | -------------> | 6 | | | +-----------+ +-----------+ | | | 7 | -------------> | 7 | | | +-----------+ +-----------+ | | | | | | +-----------+ The value of page->compound_head is the same for all tail pages. The first page of page structs (page 0) associated with the HugeTLB page contains the 4 page structs necessary to describe the HugeTLB. The only use of the remaining pages of page structs (page 1 to page 7) is to point to page->compound_head. Therefore, we can remap pages 2 to 7 to page 1. Only 2 pages of page structs will be used for each HugeTLB page. This will allow us to free the remaining 6 pages to the buddy allocator. Here is how things look after remapping. HugeTLB struct pages(8 pages) page frame(8 pages) +-----------+ ---virt_to_page---> +-----------+ mapping to +-----------+ | | | 0 | -------------> | 0 | | | +-----------+ +-----------+ | | | 1 | -------------> | 1 | | | +-----------+ +-----------+ | | | 2 | ----------------^ ^ ^ ^ ^ ^ | | +-----------+ | | | | | | | | 3 | ------------------+ | | | | | | +-----------+ | | | | | | | 4 | --------------------+ | | | | 2MB | +-----------+ | | | | | | 5 | ----------------------+ | | | | +-----------+ | | | | | 6 | ------------------------+ | | | +-----------+ | | | | 7 | --------------------------+ | | +-----------+ | | | | | | +-----------+ When a HugeTLB is freed to the buddy system, we should allocate 6 pages for vmemmap pages and restore the previous mapping relationship. Apart from 2MB HugeTLB page, we also have 1GB HugeTLB page. It is similar to the 2MB HugeTLB page. We also can use this approach to free the vmemmap pages. In this case, for the 1GB HugeTLB page, we can save 4094 pages. This is a very substantial gain. On our server, run some SPDK/QEMU applications which will use 1024GB HugeTLB page. With this feature enabled, we can save ~16GB (1G hugepage)/~12GB (2MB hugepage) memory. Because there are vmemmap page tables reconstruction on the freeing/allocating 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] = nsecs; } kretprobe:alloc_fresh_huge_page /@start[tid]/ { @latency = hist(nsecs - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [8K, 16K) 5476 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [16K, 32K) 4760 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [32K, 64K) 4 | | b) Without this patch series: # time echo 10240 > /proc/sys/vm/nr_hugepages real 0m0.067s user 0m0.000s sys 0m0.067s # bpftrace -e 'kprobe:alloc_fresh_huge_page { @start[tid] = nsecs; } kretprobe:alloc_fresh_huge_page /@start[tid]/ { @latency = hist(nsecs - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [4K, 8K) 10147 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [8K, 16K) 93 | | Summarize: this feature is about ~2x slower than before. 2) Freeing 10240 2MB HugeTLB pages. a) With this patch series applied: # time echo 0 > /proc/sys/vm/nr_hugepages real 0m0.213s user 0m0.000s sys 0m0.213s # bpftrace -e 'kprobe:free_pool_huge_page { @start[tid] = nsecs; } kretprobe:free_pool_huge_page /@start[tid]/ { @latency = hist(nsecs - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [8K, 16K) 6 | | [16K, 32K) 10227 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [32K, 64K) 7 | | b) Without this patch series: # time echo 0 > /proc/sys/vm/nr_hugepages real 0m0.081s user 0m0.000s sys 0m0.081s # bpftrace -e 'kprobe:free_pool_huge_page { @start[tid] = nsecs; } kretprobe:free_pool_huge_page /@start[tid]/ { @latency = hist(nsecs - @start[tid]); delete(@start[tid]); }' Attaching 2 probes... @latency: [4K, 8K) 6805 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [8K, 16K) 3427 |@@@@@@@@@@@@@@@@@@@@@@@@@@ | [16K, 32K) 8 | | Summarize: The overhead of __free_hugepage is about ~2-3x slower than before. Although the overhead has increased, the overhead is not significant. Like Mike said, "However, remember that the majority of use cases create HugeTLB pages at or shortly after boot time and add them to the pool. So, additional overhead 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/unmap)". Despite the overhead and in addition to the memory gains from this series. The following data is obtained by Joao Martins. Very thanks to his effort. There's an additional benefit which is page (un)pinners will see an improvement and Joao presumes because there are fewer memmap pages and thus the tail/head pages are staying in cache more often. Out of the box Joao saw (when comparing linux-next against linux-next + this series) with gup_test and pinning a 16G HugeTLB file (with 1G pages): get_user_pages(): ~32k -> ~9k unpin_user_pages(): ~75k -> ~70k Usually any tight loop fetching compound_head(), or reading tail pages data (e.g. compound_head) benefit a lot. There's some unpinning inefficiencies Joao was fixing[2], but with that in added it shows even more: unpin_user_pages(): ~27k -> ~3.8k [1] https://lore.kernel.org/linux-mm/20210409205254.242291-1-mike.kravetz@oracle.com/ [2] https://lore.kernel.org/linux-mm/20210204202500.26474-1-joao.m.martins@oracle.com/ Todo: - Free all of the tail vmemmap pages Now for the 2MB HugrTLB page, we only free 6 vmemmap pages. we really can free 7 vmemmap pages. In this case, we can see 8 of the 512 struct page structures has beed set PG_head flag. If we can adjust compound_head() slightly and make compound_head() return the real head struct page when the parameter is the tail struct page but with PG_head flag set. In order to make the code evolution route clearer. This feature can can be a separate patch after this patchset is solid. - Support for other architectures (e.g. aarch64). - Enable PMD/huge page mapping of vmemmap even if this feature was enabled. Changelog in v19 -> v20: - Rebase to next-20210412. - Introduce workqueue to defer freeing HugeTLB pages. - Remove all tags (Reviewed-by ot Tested-by) from patch 6. - Disable memmap_on_memory when hugetlb_free_vmemmap enabled (patch 8). Changelog in v18 -> v19: - Fix compiler error on sparc arch. Thanks Stephen. - Make patch "gather discrete indexes of tail page" prior to "free the vmemmap pages associated with each HugeTLB page". - Remove some BUG_ON from patch #4. - Update patch #6 changelog. - Update Documentation/admin-guide/mm/memory-hotplug.rst. - Drop the patch of "optimize the code with the help of the compiler". - Update Documentation/admin-guide/kernel-parameters.txt in patch #7. - Trim update_and_free_page. Thanks to Michal, Oscar and Mike's review and suggestions. Changelog in v17 -> v18: - Add complete copyright to bootmem_info.c (Suggested by Balbir). - Fix some issues (in patch #4) suggested by Mike. Thanks to Balbir and Mike's review. Also thanks to Chen Huang and Bodeddula Balasubramaniam's test. Changelog in v16 -> v17: - Fix issues suggested by Mike and Oscar. - Update commit log suggested by Michal. Thanks to Mike, David H and Michal's suggestions and review. Changelog in v15 -> v16: - Use GFP_KERNEL to allocate vmemmap pages. Thanks to Mike, David H and Michal's suggestions. Changelog in v14 -> v15: - Fix some issues suggested by Oscar. Thanks to Oscar. - Add numbers which Joao Martins tested to cover letter. Thanks to his effort. Changelog in v13 -> v14: - Refuse to free the HugeTLB page when the system is under memory pressure. - Use GFP_ATOMIC to allocate vmemmap pages instead of GFP_KERNEL. - Rebase to linux-next 20210202. - Fix and add some comments for vmemmap_remap_free(). Thanks to Oscar, Mike, David H and David R's suggestions and review. Changelog in v12 -> v13: - Remove VM_WARN_ON_PAGE macro. - Add more comments in vmemmap_pte_range() and vmemmap_remap_free(). Thanks to Oscar and Mike's suggestions and review. Changelog in v11 -> v12: - Move VM_WARN_ON_PAGE to a separate patch. - Call __free_hugepage() with hugetlb_lock (See patch #5.) to serialize with dissolve_free_huge_page(). It is to prepare for patch #9. - Introduce PageHugeInflight. See patch #9. Changelog in v10 -> v11: - Fix compiler error when !CONFIG_HUGETLB_PAGE_FREE_VMEMMAP. - Rework some comments and commit changes. - Rework vmemmap_remap_free() to 3 parameters. Thanks to Oscar and Mike's suggestions and review. Changelog in v9 -> v10: - Fix a bug in patch #11. Thanks to Oscar for pointing that out. - Rework some commit log or comments. Thanks Mike and Oscar for the suggestions. - Drop VMEMMAP_TAIL_PAGE_REUSE in the patch #3. Thank you very much Mike and Oscar for reviewing the code. Changelog in v8 -> v9: - Rework some code. Very thanks to Oscar. - Put all the non-hugetlb vmemmap functions under sparsemem-vmemmap.c. Changelog in v7 -> v8: - Adjust the order of patches. Very thanks to David and Oscar. Your suggestions are very valuable. Changelog in v6 -> v7: - Rebase to linux-next 20201130 - Do not use basepage mapping for vmemmap when this feature is disabled. - Rework some patchs. [PATCH v6 08/16] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page [PATCH v6 10/16] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Thanks to Oscar and Barry. Changelog in v5 -> v6: - Disable PMD/huge page mapping of vmemmap if this feature was enabled. - Simplify the first version code. Changelog in v4 -> v5: - Rework somme comments and code in the [PATCH v4 04/21] and [PATCH v4 05/21]. Thanks to Mike and Oscar's suggestions. Changelog in v3 -> v4: - Move all the vmemmap functions to hugetlb_vmemmap.c. - Make the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP default to y, if we want to disable this feature, we should disable it by a boot/kernel command line. - Remove vmemmap_pgtable_{init, deposit, withdraw}() helper functions. - Initialize page table lock for vmemmap through core_initcall mechanism. Thanks for Mike and Oscar's suggestions. Changelog in v2 -> v3: - Rename some helps function name. Thanks Mike. - Rework some code. Thanks Mike and Oscar. - Remap the tail vmemmap page with PAGE_KERNEL_RO instead of PAGE_KERNEL. Thanks Matthew. - Add some overhead analysis in the cover letter. - Use vmemap pmd table lock instead of a hugetlb specific global lock. Changelog in v1 -> v2: - Fix do not call dissolve_compound_page in alloc_huge_page_vmemmap(). - Fix some typo and code style problems. - Remove unused handle_vmemmap_fault(). - Merge some commits to one commit suggested by Mike. Muchun Song (9): mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP mm: hugetlb: gather discrete indexes of tail page mm: hugetlb: free the vmemmap pages associated with each HugeTLB page mm: hugetlb: defer freeing of HugeTLB pages mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap mm: memory_hotplug: disable memmap_on_memory when hugetlb_free_vmemmap enabled mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Documentation/admin-guide/kernel-parameters.txt | 21 ++ Documentation/admin-guide/mm/hugetlbpage.rst | 11 + Documentation/admin-guide/mm/memory-hotplug.rst | 13 ++ arch/sparc/mm/init_64.c | 1 + arch/x86/mm/init_64.c | 13 +- drivers/acpi/acpi_memhotplug.c | 1 + fs/Kconfig | 5 + include/linux/bootmem_info.h | 66 ++++++ include/linux/hugetlb.h | 46 +++- include/linux/hugetlb_cgroup.h | 19 +- include/linux/memory_hotplug.h | 27 --- include/linux/mm.h | 5 + mm/Makefile | 2 + mm/bootmem_info.c | 127 ++++++++++ mm/hugetlb.c | 157 +++++++++++-- mm/hugetlb_vmemmap.c | 297 ++++++++++++++++++++++++ mm/hugetlb_vmemmap.h | 45 ++++ mm/memory_hotplug.c | 134 ++--------- mm/sparse-vmemmap.c | 267 +++++++++++++++++++++ mm/sparse.c | 1 + 20 files changed, 1078 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