From patchwork Fri Oct 1 20:56:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 12531675 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DCC2C433EF for ; Fri, 1 Oct 2021 20:57:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84CA261390 for ; Fri, 1 Oct 2021 20:57:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232093AbhJAU6y (ORCPT ); Fri, 1 Oct 2021 16:58:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355313AbhJAU6w (ORCPT ); Fri, 1 Oct 2021 16:58:52 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B97AC0613E4 for ; Fri, 1 Oct 2021 13:57:07 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id o9-20020ac80249000000b002a0c9fd54d5so15787914qtg.4 for ; Fri, 01 Oct 2021 13:57:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=z8v1DZU38wPzEfaPMEQtWnD2dYyHJRJPqgiOSckBTzw=; b=PpTkjjcQNe1RxRDJRmZ1z4reN4nnk7PKKsM3AToSoI1yveU9TCiVXqeI9mc0IDsQIr s29QaDQb8l6W3gPt7ujgjW0xg+Ps/z4EiiBO4QgGObpv7kuwaDJLUletR2dlXFOhp5dD aE67EGha/yvLbTmwCFHKu9GEQQN/z8FBi4w/wRoPPlDKOm09VTCHjIWaxOuCartZ8MFz 9dMZ4e9R2KVCMhM19EZSc/i7ZZLDV57C3K3u5TXtkeqPrz7RdQgRw1oSejMytMuGEBBm qhRXsd8tqAS/9B7BxIfK61kXbTS5cQrv+Rc8+kw7mKZuGLOCvgd+oP9YRFppZwUrcni0 T1Xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=z8v1DZU38wPzEfaPMEQtWnD2dYyHJRJPqgiOSckBTzw=; b=34GcyPacMxXnqkvV9X72yP39oHDFonb/+hlR+58GnvAtVydRSrLLWxayjWuXClrvB0 SKWJNf5CyFQId5mu2VlgHLxv1Ljsm48Bd+/W6JJTu3yRsu2MbKL3FqmwByzInuMJ1VbZ zwSwDHxiWvYMMWoqo24i17F796rcT+kUdoIXFW28dmHamdNkn8hpPn2Oqj+09f8N7Sv4 ZyigUSR6bAQ+Gm/ybfLIopM77RhrC+DO3dRET3KbGqAe1lV/yFtebUFtro21nWUj7Ge8 lUL6F582hEX7DdWNJmeUK9WYdC2NgCcumJXUIuwP5zaCu53u7RYk6rC9rUpIgEUr9bb7 qH8w== X-Gm-Message-State: AOAM532VqBhDx8qzNBUVRhQ9y/0+1pqgvUvHxTBxk3GzLYjUT1Y42vQR FLb0YKipPZx1mf6/vWU4Slqx4kdE9m4= X-Google-Smtp-Source: ABdhPJzDd8N1bY00kgE20gIg97ih/EjnLN1aGuSpz6shr/dqTpTgnoute4EW2CDkdqpumhG1M4W2lJKAqdY= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:fbba:6ac8:d071:dcc]) (user=surenb job=sendgmr) by 2002:a05:6214:151:: with SMTP id x17mr11096796qvs.38.1633121826593; Fri, 01 Oct 2021 13:57:06 -0700 (PDT) Date: Fri, 1 Oct 2021 13:56:57 -0700 In-Reply-To: <20211001205657.815551-1-surenb@google.com> Message-Id: <20211001205657.815551-3-surenb@google.com> Mime-Version: 1.0 References: <20211001205657.815551-1-surenb@google.com> X-Mailer: git-send-email 2.33.0.800.g4c38ced690-goog Subject: [PATCH v10 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, pavel@ucw.cz, 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 at: https://lore.kernel.org/linux-mm/20210902231813.3597709-3-surenb@google.com/ changes in v10 - Changed anon_vma_name_alloc() to use struct_size() and avoid strcpy(), per Kees Cook include/linux/mm_types.h | 9 ++++++++- mm/madvise.c | 42 ++++++++++++++++++++++++++++++++++------ 2 files changed, 44 insertions(+), 7 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index f1896c9b2da9..30c571b4f8d3 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 69729930dde1..2f1ec13faaaa 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -63,6 +63,29 @@ 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 count; + + /* Add 1 for NUL terminator at the end of the anon_name->name */ + count = strlen(name) + 1; + anon_name = kmalloc(struct_size(anon_name, name, count), GFP_KERNEL); + if (anon_name) { + kref_init(&anon_name->kref); + memcpy(anon_name->name, name, count); + } + + 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 +98,7 @@ 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, @@ -84,34 +107,41 @@ 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) { /* 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;