From patchwork Tue Oct 19 21:55:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 12571165 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 6568FC433F5 for ; Tue, 19 Oct 2021 21:55:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E91C6134F for ; Tue, 19 Oct 2021 21:55:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229837AbhJSV5m (ORCPT ); Tue, 19 Oct 2021 17:57:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229843AbhJSV5f (ORCPT ); Tue, 19 Oct 2021 17:57:35 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87120C06176A for ; Tue, 19 Oct 2021 14:55:21 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id c65-20020a251c44000000b005ba81fe4944so27051931ybc.14 for ; Tue, 19 Oct 2021 14:55:21 -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=BodHs/XedRE19LJ4L+Zjt+mkuZYN0DpgQJxfmWf8jTc=; b=e0uJfr4GQD92ZjVnar+xwhyaVDFYemk6QpwUu8uZQbQE5WIhDQCwGDOqklaxET0J9j 8fZW8krnlUL11J+j8BB85/haX2KJTvaI+65QLA85WaP1dnJhRF45MHI+3eU+XqP/LUMo zxHNSu2buz6pEv3osleJOVi0SWfW6OSjz2Az3+5Firt191jXIn1fij7Te3man9yZzdUs eMO0DboA11qjvYx27k+4XlUdo2mXLg55c2fHUg6vS7PCGP1ic+G8n9UodFXnSX6j6uEg iTyBYgNf91CTqUNBjwC5zxFNx6hXIDIPlJkUTCF46UyPtuDY/ADI4UDTwFyNANc65UC/ /wkw== 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=BodHs/XedRE19LJ4L+Zjt+mkuZYN0DpgQJxfmWf8jTc=; b=Ee+lxzNjh+wp8AxT1h+D6voRlaabxhZTGs1MFnBPbTEbIQBxpohHHbiqyhqxG1HRND wT5LZvrEQ/Q46zRP1/11rhD/u5+tx/IeNzNDYfRu3GQeI7ecG5iFh91r6nGScogvzoNX 1UmqSgBV3vax97NeQX0ZrgvwWRSV5JIDBnDdDH+ljbIxYSgB5cXAPej6fPDmupd3fzNS UCXPPAqjIl3aRpwJnvATLXcROSNYrgeawD9UmI4Y7qJ2UlO2Ouf/o7dMbTDvFcQgbmIk B5JZfRENyAzFrza6QE40P21WGz8LKpzCpaWjC/NryeaqvtK2uvrkqriGXcr2IUeSXkru GOfw== X-Gm-Message-State: AOAM530EumY7KAmsQYyRV6hTpASUYFIT/+4F/7mm0jKYtVP/x0ek0nWd k1J83EGUw0VWSyf8Z6n6aeFjMR2MYRE= X-Google-Smtp-Source: ABdhPJxEUIcjpniDdTyBul61Zfc2+i0eoOlX7QeONj8Ex5lL8EJuiBJVUaueYVMilSO/LI51lXVqpJOgDKo= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:932c:247a:84c6:20f5]) (user=surenb job=sendgmr) by 2002:a25:824e:: with SMTP id d14mr44648379ybn.155.1634680520719; Tue, 19 Oct 2021 14:55:20 -0700 (PDT) Date: Tue, 19 Oct 2021 14:55:11 -0700 In-Reply-To: <20211019215511.3771969-1-surenb@google.com> Message-Id: <20211019215511.3771969-3-surenb@google.com> Mime-Version: 1.0 References: <20211019215511.3771969-1-surenb@google.com> X-Mailer: git-send-email 2.33.0.1079.g6e70778dc9-goog Subject: [PATCH v11 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/all/20211001205657.815551-3-surenb@google.com/ 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 3ad85843e924..89cd74c891fa 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 948fad92ba1b..a4e21bc56cab 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -64,6 +64,29 @@ static int madvise_need_mmap_write(int behavior) } #ifdef CONFIG_ANON_VMA_NAME +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; @@ -76,7 +99,7 @@ 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, @@ -85,34 +108,41 @@ 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;