From patchwork Wed May 4 21:44:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Zach O'Keefe X-Patchwork-Id: 12838662 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21B2FC433EF for ; Wed, 4 May 2022 21:45:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 80F376B0071; Wed, 4 May 2022 17:45:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7BD5B6B0073; Wed, 4 May 2022 17:45:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 685F86B0074; Wed, 4 May 2022 17:45:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 5A2DC6B0071 for ; Wed, 4 May 2022 17:45:00 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 275D7806FB for ; Wed, 4 May 2022 21:45:00 +0000 (UTC) X-FDA: 79429391160.02.853AD7F Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) by imf22.hostedemail.com (Postfix) with ESMTP id 6EF72C0090 for ; Wed, 4 May 2022 21:44:58 +0000 (UTC) Received: by mail-pf1-f202.google.com with SMTP id z19-20020a62d113000000b0050d183adf6fso797929pfg.19 for ; Wed, 04 May 2022 14:44:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=zFWaqKyRfHMRTl2qJrutXqePgr4ZyZ9uSVANicshh5w=; b=g4gnDpW9KUXPA9vCPbJfp6eboNZmnWKitO4HYMQKrKLZL+es89zmTwRC62S/nhS8tY ZFjjTHT13SCZ5RsjjU+LX3kAAdFqFmXqDj6c6NoVQdlkNIXnuydnT8J/t2lM5snHC6U+ Zt5cHJGWYa9zfaoufsy58GrL3tozUpsT+UhhMWQCoqDt2bCBb7cln8XcGkdmUzvGUVxD oN4nbYiNp8erSkOKLBk5JADk6k0GpfIc2OSUzney+aVl0Q0eWE+E8zyZEChdzFUpvNuw piWEXNHZL4+Wyrz6gbYNQjE4oHoTdg4hs3rVUxz2Z6iCacM3uFIVwlYpHL1PMLnZT+yL qaUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc :content-transfer-encoding; bh=zFWaqKyRfHMRTl2qJrutXqePgr4ZyZ9uSVANicshh5w=; b=35yHMmMvWbemH9YH4gcDBB8aG6BHK/dMGqGvTEvxuKLyLFOgQxOg2ewEiF26a/31MU z7iU/j1QlZ2GrbJ8LtYUx/BGa57XrCvpPF9dxMbOmHZdEd/LnKqHreDup8hR5XOPMBBr Qu6Nb2ccHHfVhm6k1nKavWES3e5ENdPiajrrigrULgdTMzk0QQQ4HtkRCCgHoItG/pqI 4KjCESAA6c+j+hdYqAx56BcAfFIdeN+DZ7ZjXL6M7uDLfnftxEPaZu8d4f4dRkCs4Czh ohssUXEwIKRvDnEUlc+uNoee4U/8GbPilHrmFlVcHYSR+4gCx6YeTxtV+V0OH4/EpOQB axfQ== X-Gm-Message-State: AOAM532jJAkRIORRsIrU0Y6lPDRROdDIM6wbpNkH9ODpQJu8RN+UtFbN m5mAcP+MBCuJOA2i1jid05KWh3K0A5mv X-Google-Smtp-Source: ABdhPJxLp3kK45UcHTTcnRw6XQVm86QafkOKj70jGZNyQtzi27p6+8ig/ibu+JA0cVsjME4ssKHYnJuiJuK/ X-Received: from zokeefe3.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:1b6]) (user=zokeefe job=sendgmr) by 2002:a17:902:bf09:b0:153:99a6:55b8 with SMTP id bi9-20020a170902bf0900b0015399a655b8mr23418938plb.142.1651700698421; Wed, 04 May 2022 14:44:58 -0700 (PDT) Date: Wed, 4 May 2022 14:44:24 -0700 Message-Id: <20220504214437.2850685-1-zokeefe@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.36.0.464.gb9c8b46e94-goog Subject: [PATCH v5 00/12] mm: userspace hugepage collapse From: "Zach O'Keefe" To: Alex Shi , David Hildenbrand , David Rientjes , Matthew Wilcox , Michal Hocko , Pasha Tatashin , Peter Xu , SeongJae Park , Song Liu , Vlastimil Babka , Yang Shi , Zi Yan , linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Arnd Bergmann , Axel Rasmussen , Chris Kennelly , Chris Zankel , Helge Deller , Hugh Dickins , Ivan Kokshaysky , "James E.J. Bottomley" , Jens Axboe , "Kirill A. Shutemov" , Matt Turner , Max Filippov , Miaohe Lin , Minchan Kim , Patrick Xia , Pavel Begunkov , Thomas Bogendoerfer , "Zach O'Keefe" X-Rspamd-Queue-Id: 6EF72C0090 X-Stat-Signature: 8h9rz8ip7jcbkn8bwxkrty1y9rkdc9cc X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=g4gnDpW9; spf=pass (imf22.hostedemail.com: domain of 32vNyYgcKCKcgVRLLMLNVVNSL.JVTSPUbe-TTRcHJR.VYN@flex--zokeefe.bounces.google.com designates 209.85.210.202 as permitted sender) smtp.mailfrom=32vNyYgcKCKcgVRLLMLNVVNSL.JVTSPUbe-TTRcHJR.VYN@flex--zokeefe.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam09 X-HE-Tag: 1651700698-832190 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: Introduction -------------------------------- This series provides a mechanism for userspace to induce a collapse of eligible ranges of memory into transparent hugepages in process context, thus permitting users to more tightly control their own hugepage utilization policy at their own expense. This idea was introduced by David Rientjes[1], and the semantics and implementation were introduced and discussed in a previous PATCH RFC[2]. Interface -------------------------------- The proposed interface adds a new madvise(2) mode, MADV_COLLAPSE, and leverages the new process_madvise(2) call. process_madvise(2) Performs a synchronous collapse of the native pages mapped by the list of iovecs into transparent hugepages. The system-wide THP sysfs settings as well as the VMA flags of the memory range being collapsed are both respected for the purposes of determining THP eligibility. THP allocation may enter direct reclaim and/or compaction. When a range spans multiple VMAs, the semantics of the collapse over of each VMA is independent from the others. Caller must have CAP_SYS_ADMIN if not acting on self. Return value follows existing process_madvise(2) conventions. A “success” indicates that all hugepage-sized/aligned regions covered by the provided range were either successfully collapsed, or were already pmd-mapped THPs. madvise(2) Equivalent to process_madvise(2) on self, with 0 returned on “success”. Current Use-Cases -------------------------------- (1) Immediately back executable text by THPs. Current support provided by CONFIG_READ_ONLY_THP_FOR_FS may take a long time on a large system which might impair services from serving at their full rated load after (re)starting. Tricks like mremap(2)'ing text onto anonymous memory to immediately realize iTLB performance prevents page sharing and demand paging, both of which increase steady state memory footprint. With MADV_COLLAPSE, we get the best of both worlds: Peak upfront performance and lower RAM footprints. Note that subsequent support for file-backed memory is required here. (2) malloc() implementations that manage memory in hugepage-sized chunks, but sometimes subrelease memory back to the system in native-sized chunks via MADV_DONTNEED; zapping the pmd. Later, when the memory is hot, the implementation could madvise(MADV_COLLAPSE) to re-back the memory by THPs to regain hugepage coverage and dTLB performance. TCMalloc is such an implementation that could benefit from this[3]. A prior study of Google internal workloads during evaluation of Temeraire, a hugepage-aware enhancement to TCMalloc, showed that nearly 20% of all cpu cycles were spent in dTLB stalls, and that increasing hugepage coverage by even small amount can help with that[4]. Future work -------------------------------- Only private anonymous memory is supported by this series. File and shmem memory support will be added later. One possible user of this functionality is a userspace agent that attempts to optimize THP utilization system-wide by allocating THPs based on, for example, task priority, task performance requirements, or heatmaps. For the latter, one idea that has already surfaced is using DAMON to identify hot regions, and driving THP collapse through a new DAMOS_COLLAPSE scheme[5]. Sequence of Patches -------------------------------- Patches 1-7 perform refactoring of collapse logic within khugepaged.c, introduce the notion of a collapse context, and add needed hooks to specialize per-collapse context functionality. Patches 8-10 introduces MADV_COLLAPSE, does some renaming, and adds process_madivse(2) support. Patches 11-13 add selftests to test the new functionality. Applies against next-20220502. Changelog -------------------------------- v4 -> v5: * Fix kernel test robot errors * 'mm/khugepaged: make hugepage allocation context-specific' -> Fix khugepaged_alloc_page() UMA definition * 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' -> Add "fallthrough" pseudo keyword to fix -Wimplicit-fallthrough v3 -> v4: * 'mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds THP' -> Dropped pmd_none() check from find_pmd_or_thp_or_none() -> Moved SCAN_PMD_MAPPED after SCAN_PMD_NULL -> Dropped from sign-offs * 'mm/khugepaged: add struct collapse_control' -> Updated commit description and some code comments -> Removed extra brackets added in khugepaged_find_target_node() * Added 'mm/khugepaged: dedup hugepage allocation and charging code' * 'mm/khugepaged: make hugepage allocation context-specific' -> Has been majorly reworked to replace ->gfp() and ->alloc_hpage() struct collapse_control hooks with a ->alloc_charge_hpage() hook which makes node-allocation, gfp flags, node scheduling, hpage allocation, and accounting/charging context-specific. -> Dropped from sign-offs * Added 'mm/khugepaged: pipe enum scan_result codes back to callers' -> Replaces 'mm/khugepaged: add struct collapse_result' * Dropped 'mm/khugepaged: add struct collapse_result' * 'mm/khugepaged: add flag to ignore khugepaged_max_ptes_*' -> Moved before 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' * 'mm/khugepaged: add flag to ignore page young/referenced requirement' -> Moved before 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' * 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' -> Moved struct collapse_control* argument to end of alloc_hpage() -> Some refactoring to rebase on top changes to struct collapse_control hook changes and other previous commits. -> Reworded commit description -> Dropped from sign-offs * 'mm/khugepaged: rename prefix of shared collapse functions' -> Renamed from 'mm/khugepaged: remove khugepaged prefix from shared collapse functions' -> Instead of dropping "khugepaged_" prefix, replace with "hpage_collapse_" -> Dropped from sign-offs * Rebased onto next-20220502 v2 -> v3: * Collapse semantics have changed: the gfp flags used for hugepage allocation now are independent of khugepaged. * Cover-letter: add primary use-cases and update description of collapse semantics. * 'mm/khugepaged: make hugepage allocation context-specific' -> Added .gfp operation to struct collapse_control * 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' -> Added madvise context .gfp implementation. -> Set scan_result appropriately on early exit due to mm exit or vma vma revalidation. -> Reword patch description * Rebased onto next-20220426 v1 -> v2: * Cover-letter clarification and added RFC -> v1 notes * Fixes issues reported by kernel test robot * 'mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds THP' -> Fixed mixed code/declarations * 'mm/khugepaged: make hugepage allocation context-specific' -> Fixed bad function signature in !NUMA && TRANSPARENT_HUGEPAGE configs -> Added doc comment to retract_page_tables() for "cc" * 'mm/khugepaged: add struct collapse_result' -> Added doc comment to retract_page_tables() for "cr" * 'mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse' -> Added MADV_COLLAPSE definitions for alpha, mips, parisc, xtensa -> Moved an "#ifdef NUMA" so that khugepaged_find_target_node() is defined in !NUMA && TRANSPARENT_HUGEPAGE configs. * 'mm/khugepaged: remove khugepaged prefix from shared collapse' functions -> Removed khugepaged prefix from khugepaged_find_target_node on L914 * Rebased onto next-20220414 RFC -> v1: * The series was significantly reworked from RFC and most patches are entirely new or reworked. * Collapse eligibility criteria has changed: MADV_COLLAPSE now respects VM_NOHUGEPAGE. * Collapse semantics have changed: the gfp flags used for hugepage allocation now match that of khugepaged for the same VMA, instead of the gfp flags used at-fault for calling process for the VMA. * Collapse semantics have changed: The collapse semantics for multiple VMAs spanning a single MADV_COLLAPSE call are now independent, whereas before the idea was to allow direct reclaim/compaction if any spanned VMA permitted so. * The process_madvise(2) flags, MADV_F_COLLAPSE_LIMITS and MADV_F_COLLAPSE_DEFRAG have been removed. * Implementation change: the RFC implemented collapse over a range of hugepages in a batched-fashion with the aim of doing multiple page table updates inside a single mmap_lock write. This has been changed, and the implementation now collapses each hugepage-aligned/sized region iteratively. This was motivated by an experiment which showed that, when multiple threads were concurrently faulting during a MADV_COLLAPSE operation, mean and tail latency to acquire mmap_lock in read for threads in the fault patch was improved by using a batch size of 1 (batch sizes of 1, 8, 16, 32 were tested)[6]. * Added: If a collapse operation fails because a page isn't found on the LRU, do a lru_add_drain_all() and retry. * Added: selftests [1] https://lore.kernel.org/all/C8C89F13-3F04-456B-BA76-DE2C378D30BF@nvidia.com/ [2] https://lore.kernel.org/linux-mm/20220308213417.1407042-1-zokeefe@google.com/ [3] https://github.com/google/tcmalloc/tree/master/tcmalloc [4] https://research.google/pubs/pub50370/ [5] https://lore.kernel.org/lkml/bcc8d9a0-81d-5f34-5e4-fcc28eb7ce@google.com/T/ [6] https://lore.kernel.org/linux-mm/CAAa6QmRc76n-dspGT7UK8DkaqZAOz-CkCsME1V7KGtQ6Yt2FqA@mail.gmail.com/ Zach O'Keefe (13): mm/khugepaged: separate hugepage preallocation and cleanup mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds THP mm/khugepaged: add struct collapse_control mm/khugepaged: make hugepage allocation context-specific mm/khugepaged: add struct collapse_result mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse mm/khugepaged: remove khugepaged prefix from shared collapse functions mm/khugepaged: add flag to ignore khugepaged_max_ptes_* mm/khugepaged: add flag to ignore page young/referenced requirement mm/madvise: add MADV_COLLAPSE to process_madvise() selftests/vm: modularize collapse selftests selftests/vm: add MADV_COLLAPSE collapse context to selftests selftests/vm: add test to verify recollapse of THPs include/linux/huge_mm.h | 12 + include/trace/events/huge_memory.h | 5 +- include/uapi/asm-generic/mman-common.h | 2 + mm/internal.h | 1 + mm/khugepaged.c | 598 ++++++++++++++++-------- mm/madvise.c | 11 +- mm/rmap.c | 15 +- tools/testing/selftests/vm/khugepaged.c | 417 +++++++++++------ 8 files changed, 702 insertions(+), 359 deletions(-)