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=-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 5802CC4320A for ; Fri, 27 Aug 2021 19:19:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4514760F58 for ; Fri, 27 Aug 2021 19:19:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231540AbhH0TUl (ORCPT ); Fri, 27 Aug 2021 15:20:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231630AbhH0TUa (ORCPT ); Fri, 27 Aug 2021 15:20:30 -0400 Received: from mail-qk1-x749.google.com (mail-qk1-x749.google.com [IPv6:2607:f8b0:4864:20::749]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D5673C061224 for ; Fri, 27 Aug 2021 12:19:13 -0700 (PDT) Received: by mail-qk1-x749.google.com with SMTP id b4-20020a3799040000b02903b899a4309cso1078922qke.14 for ; Fri, 27 Aug 2021 12:19:13 -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=92AD8OF4VIc1rlAFfcwW/pEz9e2egvqx/M9b8ZJAWpE=; b=U1r28Zn21CMYH1IWX1+CqiQPJum6eut/4WKOlqpJA4LXxU9BnjStINa9tWEQcyXqdA 2GC8K6g8qxZzYAtsKLExS6CTUdnrmUNotKOsIsb8oPbJKmVBL3yOh1aM/fZMmT7DTQKx 5FzYiOnBP4AFk1fM85v+rgAhdRIMmMctyf+b3QmPgeuh4IvzQxWVbmQs5sIMV1fbgJUO AWFMVLC+J00Jqn+jxZcgPCFZoxkthxgzrpI0Mb32Hax6smgI2qnnC+rWNH4fk6/jGYrp 0+JMPysJ0sLFnfoeUGacmt+92YG19EERqdizt0rUcvnkDJziPqvDp39iiFIhvJv2n+zA s1XQ== 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=92AD8OF4VIc1rlAFfcwW/pEz9e2egvqx/M9b8ZJAWpE=; b=ls6d4hPHplIf+9NrITovagfyYLx8JDzQJIHJDkLJ6/N7e85+ZEglJGri0BciLkvW/N LDn/B68LIdoKEvZu9IJk4ICKKsVloLwgtaqxXh+4/PK3MuNLS+Vi9vKqDdsEi/Baaa26 auUHZ1e+3GFroM72sBr9M9YctgOGuyrk8Hq7peM+5cG+KYTww6KUUsAjayKuQeTgT6RE je/OeEyobgoRfn4iM2SGnmT3CxBwwhiyxBgYuniRgsu056vGPX5QuPrqLHdX9nlUSQhZ TQzebdK65XNGJzRF5Qx4IOdkp/gjzzSaxue8a/DWwjCPV4SUgPxR/KGzScP3qXDHcYHR 4g/A== X-Gm-Message-State: AOAM532BiZsBenUz2LiYOh+dz42SQMBgHWcYBJyaI+Jfb1AuYXvlaX09 EV2oObrdVU2moxDapcx3UHNJ6rridnk= X-Google-Smtp-Source: ABdhPJwT8bSKRR/90ZvLEsSj8F7NXY06PlZN4un4/T72i/BmMxtmSrmqf3pUsR2YfyBD8tO+04YlzB+EGKU= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:fd8e:f32b:a64b:dd89]) (user=surenb job=sendgmr) by 2002:a05:6214:762:: with SMTP id f2mr11382474qvz.48.1630091952884; Fri, 27 Aug 2021 12:19:12 -0700 (PDT) Date: Fri, 27 Aug 2021 12:18:58 -0700 In-Reply-To: <20210827191858.2037087-1-surenb@google.com> Message-Id: <20210827191858.2037087-4-surenb@google.com> Mime-Version: 1.0 References: <20210827191858.2037087-1-surenb@google.com> X-Mailer: git-send-email 2.33.0.259.gc128427fd7-goog Subject: [PATCH v8 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, 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 --- include/linux/mm_types.h | 9 ++++++++- mm/madvise.c | 42 +++++++++++++++++++++++++++++++++------- 2 files changed, 43 insertions(+), 8 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 26a30f7a5228..a7361acf2921 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -302,6 +303,12 @@ 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 @@ -353,7 +360,7 @@ 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 bc029f3fca6a..32ac5dc5ebf3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -63,6 +63,27 @@ 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 = kzalloc(sizeof(*anon_name) + len + 1, + GFP_KERNEL); + 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 +96,7 @@ 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 +105,44 @@ 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 void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) { + const char *anon_name; + if (!name) { free_vma_anon_name(vma); return; } - 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; free_vma_anon_name(vma); } - vma->anon_name = kstrdup(name, GFP_KERNEL); + vma->anon_name = anon_vma_name_alloc(name); } /* -- 2.33.0.259.gc128427fd7-goog 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=-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=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 8AEBCC43214 for ; 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charset="UTF-8" Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=U1r28Zn2; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf13.hostedemail.com: domain of 3sDopYQYKCNkNPM9I6BJJBG9.7JHGDIPS-HHFQ57F.JMB@flex--surenb.bounces.google.com designates 209.85.222.201 as permitted sender) smtp.mailfrom=3sDopYQYKCNkNPM9I6BJJBG9.7JHGDIPS-HHFQ57F.JMB@flex--surenb.bounces.google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C02A9101CD6D X-Stat-Signature: 4myb6r3o4d184y8mp343yrseui86r8jb X-HE-Tag: 1630091953-431694 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: 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 --- include/linux/mm_types.h | 9 ++++++++- mm/madvise.c | 42 +++++++++++++++++++++++++++++++++------- 2 files changed, 43 insertions(+), 8 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 26a30f7a5228..a7361acf2921 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -302,6 +303,12 @@ 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 @@ -353,7 +360,7 @@ 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 bc029f3fca6a..32ac5dc5ebf3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -63,6 +63,27 @@ 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 = kzalloc(sizeof(*anon_name) + len + 1, + GFP_KERNEL); + 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 +96,7 @@ 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 +105,44 @@ 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 void replace_vma_anon_name(struct vm_area_struct *vma, const char *name) { + const char *anon_name; + if (!name) { free_vma_anon_name(vma); return; } - 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; free_vma_anon_name(vma); } - vma->anon_name = kstrdup(name, GFP_KERNEL); + vma->anon_name = anon_vma_name_alloc(name); } /* -- 2.33.0.259.gc128427fd7-goog