From patchwork Thu Sep 2 23:18:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 12473339 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 10022C433FE for ; Thu, 2 Sep 2021 23:18:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC09A60E90 for ; Thu, 2 Sep 2021 23:18:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348010AbhIBXTc (ORCPT ); Thu, 2 Sep 2021 19:19:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348009AbhIBXT3 (ORCPT ); Thu, 2 Sep 2021 19:19:29 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E14F2C061796 for ; Thu, 2 Sep 2021 16:18:23 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id q80-20020a25d953000000b0059a45a5f834so4558112ybg.22 for ; Thu, 02 Sep 2021 16:18:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=2WeVbVbWOPeuv0gWvnGWonjb29LnYgYvNCL7xfEPtdY=; b=NoG5gDVRZUZYLkdC69Sge1tzAFdVFrOxSUsQmNoV7vq2oPpVIqlb+HOfTG82C4naOr jM1gXNN8XQlG07S3EOmUFQeuW1gcZeMofaHUWf2X0D7KtYK6uu2G8yGo2/xWC1lTNSwo 3XykedzRYzlPtOajU5eolPet7ggw5AcdnKyDSNXx3+VW0kP5cMzhHIbzKrtNUH7dFi74 NsJTO4DdVMDLj6LPkU1JJ+9ipLZSLQYeZPvsanhW7gwHaAt/pwZ3Iw/hVI3ZBBkC/FiO QJaukd56F+4VO22aIJCQnoxwGH5vz06cy42IXEyNcyun0Xwm3HowQKsAM8wKJruV40SO EaKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=2WeVbVbWOPeuv0gWvnGWonjb29LnYgYvNCL7xfEPtdY=; b=SEj+ySvhiOKa2qrh4aXN2LOgCf+pdMSsC7c5BQTZtUJ1yrsyhUDo4cLq+odKpR9xZw jACd362/9et0Ujqt5Op7WU2ZDYQG8y2giPXua8O674g2LArfuTWdrSGgrVvZiP2xzHdO 5xopW/r+q6quSt3A5Zc4E8hIpJ2J0K+wkjEjP2Rg9AzoxCkNHxiRq6GtOQhTYNaXO/TV Al05FNGAag4CPjsBuo5A+z4chSXqSiu/7NQgUc/xa0D8MCbosu3cSUJbL/TtUjvGIz67 Xq8+7VvIWKe1UsU/+eyEvMQJfALHFJn/Shhg+BY68n7hb1tK1AJpdbcrVbNp7g1dZgtB yvtA== X-Gm-Message-State: AOAM533IsuSFnUO/ljtDWVgg2pTH9RfOJIg3Sv9YN0/uIShC5fk3FaZw P6el81w/KCJyy+PspXQ/rEG2SYLOlNs= X-Google-Smtp-Source: ABdhPJwK63IjY6KzOIWvlD0gI/A4jV/zg48XzkYrNXuNNAJPEQrVXYoi9ip/wNDPu5W6DlX0NSnCCeySU+w= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:556f:98c8:f567:be6]) (user=surenb job=sendgmr) by 2002:a25:2008:: with SMTP id g8mr1057773ybg.502.1630624703097; Thu, 02 Sep 2021 16:18:23 -0700 (PDT) Date: Thu, 2 Sep 2021 16:18:13 -0700 In-Reply-To: <20210902231813.3597709-1-surenb@google.com> Message-Id: <20210902231813.3597709-3-surenb@google.com> Mime-Version: 1.0 References: <20210902231813.3597709-1-surenb@google.com> X-Mailer: git-send-email 2.33.0.153.gba50c8fa24-goog Subject: [PATCH v9 3/3] mm: add anonymous vma name refcounting From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: ccross@google.com, sumit.semwal@linaro.org, mhocko@suse.com, dave.hansen@intel.com, keescook@chromium.org, willy@infradead.org, kirill.shutemov@linux.intel.com, vbabka@suse.cz, hannes@cmpxchg.org, corbet@lwn.net, viro@zeniv.linux.org.uk, rdunlap@infradead.org, kaleshsingh@google.com, peterx@redhat.com, rppt@kernel.org, peterz@infradead.org, catalin.marinas@arm.com, vincenzo.frascino@arm.com, chinwen.chang@mediatek.com, axelrasmussen@google.com, aarcange@redhat.com, jannh@google.com, apopple@nvidia.com, jhubbard@nvidia.com, yuzhao@google.com, will@kernel.org, fenghua.yu@intel.com, thunder.leizhen@huawei.com, hughd@google.com, feng.tang@intel.com, jgg@ziepe.ca, guro@fb.com, tglx@linutronix.de, krisman@collabora.com, chris.hyser@oracle.com, pcc@google.com, ebiederm@xmission.com, axboe@kernel.dk, legion@kernel.org, eb@emlix.com, gorcunov@gmail.com, songmuchun@bytedance.com, viresh.kumar@linaro.org, thomascedeno@google.com, sashal@kernel.org, cxfcosmos@gmail.com, linux@rasmusvillemoes.dk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, kernel-team@android.com, surenb@google.com Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org While forking a process with high number (64K) of named anonymous vmas the overhead caused by strdup() is noticeable. Experiments with ARM64 Android device show up to 40% performance regression when forking a process with 64k unpopulated anonymous vmas using the max name lengths vs the same process with the same number of anonymous vmas having no name. Introduce anon_vma_name refcounted structure to avoid the overhead of copying vma names during fork() and when splitting named anonymous vmas. When a vma is duplicated, instead of copying the name we increment the refcount of this structure. Multiple vmas can point to the same anon_vma_name as long as they increment the refcount. The name member of anon_vma_name structure is assigned at structure allocation time and is never changed. If vma name changes then the refcount of the original structure is dropped, a new anon_vma_name structure is allocated to hold the new name and the vma pointer is updated to point to the new structure. With this approach the fork() performance regressions is reduced 3-4x times and with usecases using more reasonable number of VMAs (a few thousand) the regressions is not measurable. Signed-off-by: Suren Baghdasaryan Reviewed-by: Kees Cook --- previous version including cover letter with test results is at: https://lore.kernel.org/linux-mm/20210827191858.2037087-1-surenb@google.com/ changes in v9 - Replaced kzalloc with kmalloc in anon_vma_name_alloc, per Rolf Eike Beer include/linux/mm_types.h | 9 ++++++++- mm/madvise.c | 43 +++++++++++++++++++++++++++++++++------- 2 files changed, 44 insertions(+), 8 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 968a1d0463d8..7feb43daee6c 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -310,6 +311,12 @@ struct vm_userfaultfd_ctx { struct vm_userfaultfd_ctx {}; #endif /* CONFIG_USERFAULTFD */ +struct anon_vma_name { + struct kref kref; + /* The name needs to be at the end because it is dynamically sized. */ + char name[]; +}; + /* * This struct describes a virtual memory area. There is one of these * per VM-area/task. A VM area is any part of the process virtual memory @@ -361,7 +368,7 @@ struct vm_area_struct { unsigned long rb_subtree_last; } shared; /* Serialized by mmap_sem. */ - char *anon_name; + struct anon_vma_name *anon_name; }; /* diff --git a/mm/madvise.c b/mm/madvise.c index 0c6d0f64d432..adc53edd3fe7 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -63,6 +63,28 @@ static int madvise_need_mmap_write(int behavior) } } +static struct anon_vma_name *anon_vma_name_alloc(const char *name) +{ + struct anon_vma_name *anon_name; + size_t len = strlen(name); + + /* Add 1 for NUL terminator at the end of the anon_name->name */ + anon_name = kmalloc(sizeof(*anon_name) + len + 1, GFP_KERNEL); + if (anon_name) { + kref_init(&anon_name->kref); + strcpy(anon_name->name, name); + } + + return anon_name; +} + +static void vma_anon_name_free(struct kref *kref) +{ + struct anon_vma_name *anon_name = + container_of(kref, struct anon_vma_name, kref); + kfree(anon_name); +} + static inline bool has_vma_anon_name(struct vm_area_struct *vma) { return !vma->vm_file && vma->anon_name; @@ -75,7 +97,7 @@ const char *vma_anon_name(struct vm_area_struct *vma) mmap_assert_locked(vma->vm_mm); - return vma->anon_name; + return vma->anon_name->name; } void dup_vma_anon_name(struct vm_area_struct *orig_vma, @@ -84,37 +106,44 @@ void dup_vma_anon_name(struct vm_area_struct *orig_vma, if (!has_vma_anon_name(orig_vma)) return; - new_vma->anon_name = kstrdup(orig_vma->anon_name, GFP_KERNEL); + kref_get(&orig_vma->anon_name->kref); + new_vma->anon_name = orig_vma->anon_name; } void free_vma_anon_name(struct vm_area_struct *vma) { + struct anon_vma_name *anon_name; + if (!has_vma_anon_name(vma)) return; - kfree(vma->anon_name); + anon_name = vma->anon_name; vma->anon_name = NULL; + kref_put(&anon_name->kref, vma_anon_name_free); } /* mmap_lock should be write-locked */ static int replace_vma_anon_name(struct vm_area_struct *vma, const char *name) { + const char *anon_name; + if (!name) { free_vma_anon_name(vma); return 0; } - if (vma->anon_name) { + anon_name = vma_anon_name(vma); + if (anon_name) { /* Should never happen, to dup use dup_vma_anon_name() */ - WARN_ON(vma->anon_name == name); + WARN_ON(anon_name == name); /* Same name, nothing to do here */ - if (!strcmp(name, vma->anon_name)) + if (!strcmp(name, anon_name)) return 0; free_vma_anon_name(vma); } - vma->anon_name = kstrdup(name, GFP_KERNEL); + vma->anon_name = anon_vma_name_alloc(name); if (!vma->anon_name) return -ENOMEM;