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[2620:137:e000::1:20]) by mx.google.com with ESMTP id p13-20020a056a000a0d00b00679a6ce03f6si1737376pfh.59.2023.08.10.07.54.29; Thu, 10 Aug 2023 07:54:44 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235704AbjHJO3z (ORCPT + 99 others); Thu, 10 Aug 2023 10:29:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234033AbjHJO3y (ORCPT ); Thu, 10 Aug 2023 10:29:54 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7B38F26BA for ; Thu, 10 Aug 2023 07:29:53 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D555D75; Thu, 10 Aug 2023 07:30:35 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E2083F64C; Thu, 10 Aug 2023 07:29:50 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , Matthew Wilcox , Yin Fengwei , David Hildenbrand , Yu Zhao , Catalin Marinas , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain , Itaru Kitayama , "Kirill A. Shutemov" Cc: Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 0/5] variable-order, large folios for anonymous memory Date: Thu, 10 Aug 2023 15:29:37 +0100 Message-Id: <20230810142942.3169679-1-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1773854297425973080 X-GMAIL-MSGID: 1773854297425973080 Hi All, This is v5 of a series to implement variable order, large folios for anonymous memory. (currently called "LARGE_ANON_FOLIO", previously called "FLEXIBLE_THP"). The objective of this is to improve performance by allocating larger chunks of memory during anonymous page faults: 1) Since SW (the kernel) is dealing with larger chunks of memory than base pages, there are efficiency savings to be had; fewer page faults, batched PTE and RMAP manipulation, reduced lru list, etc. In short, we reduce kernel overhead. This should benefit all architectures. 2) Since we are now mapping physically contiguous chunks of memory, we can take advantage of HW TLB compression techniques. A reduction in TLB pressure speeds up kernel and user space. arm64 systems have 2 mechanisms to coalesce TLB entries; "the contiguous bit" (architectural) and HPA (uarch). This patch set deals with the SW side of things (1). (2) is being tackled in a separate series. The new behaviour is hidden behind a new Kconfig switch, LARGE_ANON_FOLIO, which is disabled by default. Although the eventual aim is to enable it by default. My hope is that we are pretty much there with the changes at this point; hopefully this is sufficient to get an initial version merged so that we can scale up characterization efforts. Although they should not be merged until the prerequisites are complete. These are in progress and tracked at [5]. This series is based on mm-unstable (ad3232df3e41). I'm going to be out on holiday from the end of today, returning on 29th August. So responses will likely be patchy, as I'm terrified of posting to list from my phone! Testing ------- This version adds patches to mm selftests so that the cow tests explicitly test large anon folios, in the same way that thp is tested. When enabled you should see something similar at the start of the test suite: # [INFO] detected large anon folio size: 32 KiB Then the following results are expected. The fails and skips are due to existing issues in mm-unstable: # Totals: pass:207 fail:16 xfail:0 xpass:0 skip:85 error:0 Existing mm selftests reveal 1 regression in khugepaged tests when LARGE_ANON_FOLIO is enabled: Run test: collapse_max_ptes_none (khugepaged:anon) Maybe collapse with max_ptes_none exceeded.... Fail Unexpected huge page I believe this is because khugepaged currently skips non-order-0 pages when looking for collapse opportunities and should get fixed with the help of DavidH's work to create a mechanism to precisely determine shared vs exclusive pages. Changes since v4 [4] -------------------- - Removed "arm64: mm: Override arch_wants_pte_order()" patch; arm64 now uses the default order-3 size. I have moved this patch over to the contpte series. - Added "mm: Allow deferred splitting of arbitrary large anon folios" back into series. I originally removed this at v2 to add to a separate series, but that series has transformed significantly and it no longer fits, so bringing it back here. - Reintroduced dependency on set_ptes(); Originally dropped this at v2, but set_ptes() is in mm-unstable now. - Updated policy for when to allocate LAF; only fallback to order-0 if MADV_NOHUGEPAGE is present or if THP disabled via prctl; no longer rely on sysfs's never/madvise/always knob. - Fallback to order-0 whenever uffd is armed for the vma, not just when uffd-wp is set on the pte. - alloc_anon_folio() now returns `strucxt folio *`, where errors are encoded with ERR_PTR(). The last 3 changes were proposed by Yu Zhao - thanks! Changes since v3 [3] -------------------- - Renamed feature from FLEXIBLE_THP to LARGE_ANON_FOLIO. - Removed `flexthp_unhinted_max` boot parameter. Discussion concluded that a sysctl is preferable but we will wait until real workload needs it. - Fixed uninitialized `addr` on read fault path in do_anonymous_page(). - Added mm selftests for large anon folios in cow test suite. Changes since v2 [2] -------------------- - Dropped commit "Allow deferred splitting of arbitrary large anon folios" - Huang, Ying suggested the "batch zap" work (which I dropped from this series after v1) is a prerequisite for merging FLXEIBLE_THP, so I've moved the deferred split patch to a separate series along with the batch zap changes. I plan to submit this series early next week. - Changed folio order fallback policy - We no longer iterate from preferred to 0 looking for acceptable policy - Instead we iterate through preferred, PAGE_ALLOC_COSTLY_ORDER and 0 only - Removed vma parameter from arch_wants_pte_order() - Added command line parameter `flexthp_unhinted_max` - clamps preferred order when vma hasn't explicitly opted-in to THP - Never allocate large folio for MADV_NOHUGEPAGE vma (or when THP is disabled for process or system). - Simplified implementation and integration with do_anonymous_page() - Removed dependency on set_ptes() Changes since v1 [1] -------------------- - removed changes to arch-dependent vma_alloc_zeroed_movable_folio() - replaced with arch-independent alloc_anon_folio() - follows THP allocation approach - no longer retry with intermediate orders if allocation fails - fallback directly to order-0 - remove folio_add_new_anon_rmap_range() patch - instead add its new functionality to folio_add_new_anon_rmap() - remove batch-zap pte mappings optimization patch - remove enabler folio_remove_rmap_range() patch too - These offer real perf improvement so will submit separately - simplify Kconfig - single FLEXIBLE_THP option, which is independent of arch - depends on TRANSPARENT_HUGEPAGE - when enabled default to max anon folio size of 64K unless arch explicitly overrides - simplify changes to do_anonymous_page(): - no more retry loop [1] https://lore.kernel.org/linux-mm/20230626171430.3167004-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-mm/20230703135330.1865927-1-ryan.roberts@arm.com/ [3] https://lore.kernel.org/linux-mm/20230714160407.4142030-1-ryan.roberts@arm.com/ [4] https://lore.kernel.org/linux-mm/20230726095146.2826796-1-ryan.roberts@arm.com/ [5] https://lore.kernel.org/linux-mm/f8d47176-03a8-99bf-a813-b5942830fd73@arm.com/ Thanks, Ryan Ryan Roberts (5): mm: Allow deferred splitting of arbitrary large anon folios mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap() mm: LARGE_ANON_FOLIO for improved performance selftests/mm/cow: Generalize do_run_with_thp() helper selftests/mm/cow: Add large anon folio tests include/linux/pgtable.h | 13 ++ mm/Kconfig | 10 ++ mm/memory.c | 144 +++++++++++++++++-- mm/rmap.c | 31 +++-- tools/testing/selftests/mm/cow.c | 229 ++++++++++++++++++++++--------- 5 files changed, 347 insertions(+), 80 deletions(-) --- 2.25.1