From patchwork Fri May 19 19:09:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 684161 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32AF9C7EE29 for ; Fri, 19 May 2023 19:10:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231739AbjESTK1 (ORCPT ); Fri, 19 May 2023 15:10:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231555AbjESTKI (ORCPT ); Fri, 19 May 2023 15:10:08 -0400 Received: from mail-vs1-xe2b.google.com (mail-vs1-xe2b.google.com [IPv6:2607:f8b0:4864:20::e2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13B4210FA for ; Fri, 19 May 2023 12:09:48 -0700 (PDT) Received: by mail-vs1-xe2b.google.com with SMTP id ada2fe7eead31-42c38a6daf3so2289150137.3 for ; Fri, 19 May 2023 12:09:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1684523387; x=1687115387; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=oA7dMwlFmxPwFfHcKnUeZ7hJdv/AmQxUS93JuDL6gPU=; b=PCCuvdHXc4XusTKOuKnfHxqjmcKF33HedUvjSSIEB/LXCB8ftanEMvL27R617BEABE Y/SPIH6C+KoN5BEgulkLv5sqTuTF5fabGZNZo/HEVlSSY07Ygemgsus3/woEkmwUHdjS jaexiTko+LYiXNXWhDhnPmbUFhCF0ImXBUCV8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684523387; x=1687115387; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=oA7dMwlFmxPwFfHcKnUeZ7hJdv/AmQxUS93JuDL6gPU=; b=TyYjj2mmwhu+3olCKEmDHmuE/FvzYYURfpQKOdK754fVc6LVysnybWySKPN0ETeH5Y WT4WRnOOPm/Cyim1yLHrqwnew53mn4v47aElUabe7iFoddwhbKVbKqnPQ2mFMybvcQam A+y6nmhKTg7vtpjcVFsIuvhz03UX1n0Se17jLPqN9cATpYlNOKZS9KOPZEu7XY5KjFJ0 fbIY+pJ32yBxqTaK5AYYfZDRI92zMTFUl4sGadK18jBAzm+n2h2pT6MqqA4yiqi47lko NJjSIiEdPAkFbIZKn2Bl03wkSA0GonB8zB1FIuCHK9yvpemc9R27uEQ1EXjyn8dvLx2L jtdQ== X-Gm-Message-State: AC+VfDxIR6Raf5V7WxVgvI0gfC99WjTFJGHxTGUSgLXBrgJR2pEq6adp UrxVsYysWjSKA/OxsS7xcQAArA== X-Google-Smtp-Source: ACHHUZ5tNnkzlczdh01+L99WDBDunQiDAPpU6vp4udkIFHQy9fkqGeBYT8FDX47Do14GAQyh+6aSSA== X-Received: by 2002:a05:6102:2ca:b0:436:2c6f:207f with SMTP id h10-20020a05610202ca00b004362c6f207fmr199261vsh.6.1684523386917; Fri, 19 May 2023 12:09:46 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (129.239.188.35.bc.googleusercontent.com. [35.188.239.129]) by smtp.gmail.com with ESMTPSA id q20-20020ae9e414000000b0074e1ee30478sm1317611qkc.37.2023.05.19.12.09.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 May 2023 12:09:46 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Linus Torvalds , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan Subject: [PATCH v2 1/4] mm/mremap: Optimize the start addresses in move_page_tables() Date: Fri, 19 May 2023 19:09:31 +0000 Message-ID: <20230519190934.339332-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.698.g37aff9b760-goog In-Reply-To: <20230519190934.339332-1-joel@joelfernandes.org> References: <20230519190934.339332-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Recently, we see reports [1] of a warning that triggers due to move_page_tables() doing a downward and overlapping move on a mutually-aligned offset within a PMD. By mutual alignment, I mean the source and destination addresses of the mremap are at the same offset within a PMD. This mutual alignment along with the fact that the move is downward is sufficient to cause a warning related to having an allocated PMD that does not have PTEs in it. This warning will only trigger when there is mutual alignment in the move operation. A solution, as suggested by Linus Torvalds [2], is to initiate the copy process at the PMD level whenever such alignment is present. Implementing this approach will not only prevent the warning from being triggered, but it will also optimize the operation as this method should enhance the speed of the copy process whenever there's a possibility to start copying at the PMD level. Some more points: a. The optimization can be done only when both the source and destination of the mremap do not have anything mapped below it up to a PMD boundary. I add support to detect that. b. #1 is not a problem for the call to move_page_tables() from exec.c as nothing is expected to be mapped below the source/destination. However, for non-overlapping mutually aligned moves as triggered by mremap(2), I added support for checking such cases. c. I currently only optimize for PMD moves, in the future I/we can build on this work and do PUD moves as well if there is a need for this. But I want to take it one step at a time. [1] https://lore.kernel.org/all/ZB2GTBD%2FLWTrkOiO@dhcp22.suse.cz/ [2] https://lore.kernel.org/all/CAHk-=whd7msp8reJPfeGNyt0LiySMT0egExx3TVZSX3Ok6X=9g@mail.gmail.com/ Suggested-by: Linus Torvalds Signed-off-by: Joel Fernandes (Google) --- mm/mremap.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index 411a85682b58..be81eb3a80a8 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -478,6 +478,51 @@ static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, return moved; } +/* + * A helper to check if a previous mapping exists. Required for + * move_page_tables() and realign_addr() to determine if a previous mapping + * exists before we can do realignment optimizations. + */ +static bool check_addr_in_prev(struct vm_area_struct *vma, unsigned long addr, + unsigned long mask) +{ + int addr_masked = addr & mask; + struct vm_area_struct *prev = NULL, *cur = NULL; + + /* If the masked address is within vma, there is no prev mapping of concern. */ + if (vma->vm_start <= addr_masked) + return false; + + /* + * Attempt to find vma before prev that contains the address. + * On any issue, assume the address is within a previous mapping. + * @mmap write lock is held here, so the lookup is safe. + */ + cur = find_vma_prev(vma->vm_mm, vma->vm_start, &prev); + if (!cur || cur != vma || !prev) + return true; + + /* The masked address fell within a previous mapping. */ + if (prev->vm_end > addr_masked) + return true; + + return false; +} + +/* Opportunistically realign to specified boundary for faster copy. */ +static void realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma, + unsigned long *new_addr, struct vm_area_struct *new_vma, + unsigned long mask) +{ + if ((*old_addr & ~mask) && + (*old_addr & ~mask) == (*new_addr & ~mask) && + !check_addr_in_prev(old_vma, *old_addr, mask) && + !check_addr_in_prev(new_vma, *new_addr, mask)) { + *old_addr = *old_addr & mask; + *new_addr = *new_addr & mask; + } +} + unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long old_addr, struct vm_area_struct *new_vma, unsigned long new_addr, unsigned long len, @@ -493,6 +538,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma, old_end = old_addr + len; + /* If possible, realign addresses to PMD boundary for faster copy. */ + if (len >= PMD_SIZE - (old_addr & ~PMD_MASK)) + realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK); + if (is_vm_hugetlb_page(vma)) return move_hugetlb_page_tables(vma, new_vma, old_addr, new_addr, len); @@ -565,6 +614,13 @@ unsigned long move_page_tables(struct vm_area_struct *vma, mmu_notifier_invalidate_range_end(&range); + /* + * Prevent negative return values when {old,new}_addr was realigned + * but we broke out of the above loop for the first PMD itself. + */ + if (len + old_addr < old_end) + return 0; + return len + old_addr - old_end; /* how much done */ } From patchwork Fri May 19 19:09:33 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 684160 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC38DC7EE2D for ; Fri, 19 May 2023 19:10:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231499AbjESTK3 (ORCPT ); Fri, 19 May 2023 15:10:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231616AbjESTKX (ORCPT ); Fri, 19 May 2023 15:10:23 -0400 Received: from mail-ua1-x92a.google.com (mail-ua1-x92a.google.com [IPv6:2607:f8b0:4864:20::92a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E543110F8 for ; Fri, 19 May 2023 12:09:49 -0700 (PDT) Received: by mail-ua1-x92a.google.com with SMTP id a1e0cc1a2514c-783f88ce557so2057896241.3 for ; 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[35.188.239.129]) by smtp.gmail.com with ESMTPSA id q20-20020ae9e414000000b0074e1ee30478sm1317611qkc.37.2023.05.19.12.09.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 May 2023 12:09:48 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan Subject: [PATCH v2 3/4] selftests: mm: Add a test for mutually aligned moves > PMD size Date: Fri, 19 May 2023 19:09:33 +0000 Message-ID: <20230519190934.339332-4-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.698.g37aff9b760-goog In-Reply-To: <20230519190934.339332-1-joel@joelfernandes.org> References: <20230519190934.339332-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org This patch adds a test case to check if a PMD-alignment optimization successfully happens. I add support to make sure there is some room before the source mapping, otherwise the optimization to trigger PMD-aligned move will be disabled as the kernel will detect that a mapping before the source exists and such optimization becomes impossible. Signed-off-by: Joel Fernandes (Google) --- tools/testing/selftests/mm/mremap_test.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c index 6822d657f589..6304eb0947a3 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -44,6 +44,7 @@ enum { _1MB = 1ULL << 20, _2MB = 2ULL << 20, _4MB = 4ULL << 20, + _5MB = 5ULL << 20, _1GB = 1ULL << 30, _2GB = 2ULL << 30, PMD = _2MB, @@ -235,6 +236,11 @@ static void *get_source_mapping(struct config c) unsigned long long mmap_min_addr; mmap_min_addr = get_mmap_min_addr(); + /* + * For some tests, we need to not have any mappings below the + * source mapping. Add some headroom to mmap_min_addr for this. + */ + mmap_min_addr += 10 * _4MB; retry: addr += c.src_alignment; @@ -434,7 +440,7 @@ static int parse_args(int argc, char **argv, unsigned int *threshold_mb, return 0; } -#define MAX_TEST 13 +#define MAX_TEST 14 #define MAX_PERF_TEST 3 int main(int argc, char **argv) { @@ -500,6 +506,10 @@ int main(int argc, char **argv) test_cases[12] = MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS, "2GB mremap - Source PUD-aligned, Destination PUD-aligned"); + /* Src and Dest addr 1MB aligned. 5MB mremap. */ + test_cases[13] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS, + "5MB mremap - Source 1MB-aligned, Destination 1MB-aligned"); + perf_test_cases[0] = MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS, "1GB mremap - Source PTE-aligned, Destination PTE-aligned"); /*