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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 D3EF7C433FE for ; Wed, 22 Sep 2021 10:27:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB1DF611C9 for ; Wed, 22 Sep 2021 10:27:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234865AbhIVK2v (ORCPT ); Wed, 22 Sep 2021 06:28:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234864AbhIVK2u (ORCPT ); Wed, 22 Sep 2021 06:28:50 -0400 Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C10B9C061574 for ; Wed, 22 Sep 2021 03:27:20 -0700 (PDT) Received: by mail-pj1-x102a.google.com with SMTP id z14-20020a17090a8b8e00b0019cc29ceef1so4143625pjn.1 for ; Wed, 22 Sep 2021 03:27:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=4dXtWvh0hz8AcEkJtaCmZCNKq+swCjTc/s3IW/xzmY0=; b=iY1pxp/2LjuDMZjmTZVAm7zcKIrGCkGDzB8F60/vWyJhBG5OcZHTnCVHmQ3RK7R2Bt FFLnNjzE9DjpjGDHrYEMi59CeaVszgVi/h+w79XXPo51qdU/iWCogjk/3z0yHWmiW+84 uPemc83b+vwRqo1cGqWQbgzc4CamH74Cq5foB+wUHiTeS48b10l4tzL4nHUMZ5Q/QHJH 9XFvlg96N6gmgQXCaZTsPganY668ZQvB5F+R3tif8zFXelLPKbHfkYebnNXrFVMTjAGn XiWwgmCpsoIeKXqf17NPnrIEloRe90Aarlv0+8gKhzjnzgyNgmU6dBk30xxHujB9m1zo l90g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=4dXtWvh0hz8AcEkJtaCmZCNKq+swCjTc/s3IW/xzmY0=; b=rB1AMDFmLeu0qDKmU4pIxNV7BFHcBUCkGwF9zpvVnRy6Ymz/IfIbUIxEg6xPffhrIL BjlyRk0b23Hkw7Pk4e6N8LR9QtpFmbap3Kg8A+zo5fzyPyfU9vJ+126Bx/ctQhQcflhj C59xuCNnEdh2SrrFSiIrpkvQHkS2XKafAc6qTibESNB5UwQUWJVUB25GOWDQYqQzKS8n a52Yvkos4xayvxC5vPt7nlBWCYNN4uNCjPpIFxJCcBjCUKNrEawRmct/SwTzRRnZzfmG iuE5eaOYPPO25kdCfsQAac7/zPOR5UqV/AoGviA4RATlGCvWQAqy2Dar4+nbLWxhiHxE VeHQ== X-Gm-Message-State: AOAM5316pEvZgIHeC2EN/QLkbRJEVtecG6DxpyD4u6COfSidDz6GMy9p rRmP1STHMxEJ+QZdOTs7sI96jA== X-Google-Smtp-Source: ABdhPJxC+8sPcMCYb0LCoNN2Yblp/Tq/ZoiWIgS7Vo0HeqiB0K1B/lTrvFsHWyH/3dUXCrgzLLFZfg== X-Received: by 2002:a17:90b:4b4b:: with SMTP id mi11mr10255208pjb.41.1632306440284; Wed, 22 Sep 2021 03:27:20 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.255]) by smtp.gmail.com with ESMTPSA id s89sm1821929pjj.43.2021.09.22.03.27.14 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Sep 2021 03:27:20 -0700 (PDT) From: Muchun Song To: mike.kravetz@oracle.com, akpm@linux-foundation.org, osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com, chenhuang5@huawei.com, bodeddub@amazon.com, corbet@lwn.net, willy@infradead.org, 21cnbao@gmail.com Cc: duanxiongchun@bytedance.com, fam.zheng@bytedance.com, smuchun@gmail.com, zhengqi.arch@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song Subject: [PATCH v3 3/4] mm: sparsemem: use page table lock to protect kernel pmd operations Date: Wed, 22 Sep 2021 18:24:10 +0800 Message-Id: <20210922102411.34494-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210922102411.34494-1-songmuchun@bytedance.com> References: <20210922102411.34494-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org The init_mm.page_table_lock is used to protect kernel page tables, we can use it to serialize splitting vmemmap PMD mappings instead of mmap write lock, which can increase the concurrency of vmemmap_remap_free(). Actually, It increase the concurrency between allocations of HugeTLB pages. But it is not the only benefit. There are a lot of users of mmap read lock of init_mm. The mmap write lock is holding through vmemmap_remap_free(), removing mmap write lock usage to make it does not affect other users of mmap read lock. It is not making anything worse and always a win to move. Signed-off-by: Muchun Song --- mm/ptdump.c | 16 ++++++++++++---- mm/sparse-vmemmap.c | 49 ++++++++++++++++++++++++++++++++++--------------- 2 files changed, 46 insertions(+), 19 deletions(-) diff --git a/mm/ptdump.c b/mm/ptdump.c index da751448d0e4..eea3d28d173c 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -40,8 +40,10 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr, if (st->effective_prot) st->effective_prot(st, 0, pgd_val(val)); - if (pgd_leaf(val)) + if (pgd_leaf(val)) { st->note_page(st, addr, 0, pgd_val(val)); + walk->action = ACTION_CONTINUE; + } return 0; } @@ -61,8 +63,10 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr, if (st->effective_prot) st->effective_prot(st, 1, p4d_val(val)); - if (p4d_leaf(val)) + if (p4d_leaf(val)) { st->note_page(st, addr, 1, p4d_val(val)); + walk->action = ACTION_CONTINUE; + } return 0; } @@ -82,8 +86,10 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr, if (st->effective_prot) st->effective_prot(st, 2, pud_val(val)); - if (pud_leaf(val)) + if (pud_leaf(val)) { st->note_page(st, addr, 2, pud_val(val)); + walk->action = ACTION_CONTINUE; + } return 0; } @@ -101,8 +107,10 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr, if (st->effective_prot) st->effective_prot(st, 3, pmd_val(val)); - if (pmd_leaf(val)) + if (pmd_leaf(val)) { st->note_page(st, addr, 3, pmd_val(val)); + walk->action = ACTION_CONTINUE; + } return 0; } diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index 62e3d20648ce..e636943ccfc4 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -64,8 +64,8 @@ struct vmemmap_remap_walk { */ #define NR_RESET_STRUCT_PAGE 3 -static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, - struct vmemmap_remap_walk *walk) +static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, + struct vmemmap_remap_walk *walk) { pmd_t __pmd; int i; @@ -87,15 +87,37 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, set_pte_at(&init_mm, addr, pte, entry); } - /* Make pte visible before pmd. See comment in __pte_alloc(). */ - smp_wmb(); - pmd_populate_kernel(&init_mm, pmd, pgtable); + spin_lock(&init_mm.page_table_lock); + if (likely(pmd_leaf(*pmd))) { + /* Make pte visible before pmd. See comment in __pte_alloc(). */ + smp_wmb(); + pmd_populate_kernel(&init_mm, pmd, pgtable); + flush_tlb_kernel_range(start, start + PMD_SIZE); + spin_unlock(&init_mm.page_table_lock); - flush_tlb_kernel_range(start, start + PMD_SIZE); + return 0; + } + spin_unlock(&init_mm.page_table_lock); + pte_free_kernel(&init_mm, pgtable); return 0; } +static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, + struct vmemmap_remap_walk *walk) +{ + int ret; + + spin_lock(&init_mm.page_table_lock); + ret = pmd_leaf(*pmd); + spin_unlock(&init_mm.page_table_lock); + + if (ret) + ret = __split_vmemmap_huge_pmd(pmd, start, walk); + + return ret; +} + static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) @@ -132,13 +154,12 @@ static int vmemmap_pmd_range(pud_t *pud, unsigned long addr, pmd = pmd_offset(pud, addr); do { - if (pmd_leaf(*pmd)) { - int ret; + int ret; + + ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK, walk); + if (ret) + return ret; - ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK, walk); - if (ret) - return ret; - } next = pmd_addr_end(addr, end); vmemmap_pte_range(pmd, addr, next, walk); } while (pmd++, addr = next, addr != end); @@ -321,10 +342,8 @@ int vmemmap_remap_free(unsigned long start, unsigned long end, */ BUG_ON(start - reuse != PAGE_SIZE); - mmap_write_lock(&init_mm); + mmap_read_lock(&init_mm); ret = vmemmap_remap_range(reuse, end, &walk); - mmap_write_downgrade(&init_mm); - if (ret && walk.nr_walked) { end = reuse + walk.nr_walked * PAGE_SIZE; /* -- 2.11.0