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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 45534C56202 for ; Fri, 13 Nov 2020 01:12:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 850802224E for ; Fri, 13 Nov 2020 01:12:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="PWTfj3iq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 850802224E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B31C46B005C; Thu, 12 Nov 2020 20:12:42 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AE2EF6B005D; Thu, 12 Nov 2020 20:12:42 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9AA706B0068; Thu, 12 Nov 2020 20:12:42 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0152.hostedemail.com [216.40.44.152]) by kanga.kvack.org (Postfix) with ESMTP id 6D3366B005C for ; Thu, 12 Nov 2020 20:12:42 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 16671180AD804 for ; Fri, 13 Nov 2020 01:12:42 +0000 (UTC) X-FDA: 77477620164.09.bite21_0c072972730a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id F374F180AD802 for ; Fri, 13 Nov 2020 01:12:41 +0000 (UTC) X-HE-Tag: bite21_0c072972730a X-Filterd-Recvd-Size: 7906 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Fri, 13 Nov 2020 01:12:41 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E3D9E216C4; Fri, 13 Nov 2020 01:12:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605229960; bh=o0IqKrqlUm9rsrEKhbQDRYDb/kwkh0twQ4jVI7TjfLc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=PWTfj3iqj8Gr8cnGKSFZTMCB+6fY4qsJ8ptSoVbHd1IEw4b/btJMMfWioGdzfg/zv WGPaDKECoaB6Zxq0waGoVqN2sDKAp3bEOcPk5ORIvvQ2Jh/mbFSebVoxTRXH2QsgUt JIsa5kvHUQbnLCyolERQagFXGta9wHxG9hkN+3G8= Date: Thu, 12 Nov 2020 17:12:39 -0800 From: Andrew Morton To: Roman Gushchin Cc: Johannes Weiner , , Shakeel Butt , Michal Hocko , Christoph Lameter , , Subject: Re: [PATCH 2/2] mm: memcg/slab: pre-allocate obj_cgroups for slab caches with SLAB_ACCOUNT Message-Id: <20201112171239.4f8ef107f741c3462556731f@linux-foundation.org> In-Reply-To: <20201113001926.GA2934489@carbon.dhcp.thefacebook.com> References: <20201110195753.530157-1-guro@fb.com> <20201110195753.530157-2-guro@fb.com> <20201112162303.GB873621@cmpxchg.org> <20201113001926.GA2934489@carbon.dhcp.thefacebook.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: On Thu, 12 Nov 2020 16:19:26 -0800 Roman Gushchin wrote: > >From 8b28d91475d54c552e503e66f169e1e00475c856 Mon Sep 17 00:00:00 2001 > From: Roman Gushchin > Date: Wed, 16 Sep 2020 15:43:48 -0700 > Subject: [PATCH v2 2/2] mm: memcg/slab: pre-allocate obj_cgroups for slab > caches with SLAB_ACCOUNT > > In general it's unknown in advance if a slab page will contain > accounted objects or not. In order to avoid memory waste, an > obj_cgroup vector is allocated dynamically when a need to account > of a new object arises. Such approach is memory efficient, but > requires an expensive cmpxchg() to set up the memcg/objcgs pointer, > because an allocation can race with a different allocation on another > cpu. > > But in some common cases it's known for sure that a slab page will > contain accounted objects: if the page belongs to a slab cache with a > SLAB_ACCOUNT flag set. It includes such popular objects like > vm_area_struct, anon_vma, task_struct, etc. > > In such cases we can pre-allocate the objcgs vector and simple assign > it to the page without any atomic operations, because at this early > stage the page is not visible to anyone else. > > v2: inline set_page_objcgs() and add some comments, by Johannes Had me confused! I was looking for the inlined function set_page_objcgs(). I think "open-code" is a better term here than "inline". Here's the -fix: From: Roman Gushchin Subject: mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account-v2 open-code set_page_objcgs() and add some comments, by Johannes Link: https://lkml.kernel.org/r/20201113001926.GA2934489@carbon.dhcp.thefacebook.com Signed-off-by: Roman Gushchin Cc: Christoph Lameter Cc: Johannes Weiner Cc: Michal Hocko Cc: Shakeel Butt Signed-off-by: Andrew Morton --- include/linux/memcontrol.h | 25 ------------------------- mm/memcontrol.c | 23 +++++++++++++++++++---- mm/slab.h | 8 ++++---- 3 files changed, 23 insertions(+), 33 deletions(-) --- a/include/linux/memcontrol.h~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account-v2 +++ a/include/linux/memcontrol.h @@ -480,25 +480,6 @@ static inline struct obj_cgroup **page_o return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } -/* - * set_page_objcgs - associate a page with a object cgroups vector - * @page: a pointer to the page struct - * @objcgs: a pointer to the object cgroups vector - * @atomic: save the value atomically - * - * Atomically associates a page with a vector of object cgroups. - */ -static inline bool set_page_objcgs(struct page *page, - struct obj_cgroup **objcgs, bool atomic) -{ - unsigned long memcg_data = (unsigned long) objcgs | MEMCG_DATA_OBJCGS; - - if (atomic) - return !cmpxchg(&page->memcg_data, 0, memcg_data); - - page->memcg_data = memcg_data; - return true; -} #else static inline struct obj_cgroup **page_objcgs(struct page *page) { @@ -509,12 +490,6 @@ static inline struct obj_cgroup **page_o { return NULL; } - -static inline bool set_page_objcgs(struct page *page, - struct obj_cgroup **objcgs, bool atomic) -{ - return true; -} #endif static __always_inline bool memcg_stat_item_in_bytes(int idx) --- a/mm/memcontrol.c~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account-v2 +++ a/mm/memcontrol.c @@ -2879,9 +2879,10 @@ static void commit_charge(struct page *p #ifdef CONFIG_MEMCG_KMEM int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, - gfp_t gfp, bool atomic) + gfp_t gfp, bool new_page) { unsigned int objects = objs_per_slab_page(s, page); + unsigned long memcg_data; void *vec; vec = kcalloc_node(objects, sizeof(struct obj_cgroup *), gfp, @@ -2889,11 +2890,25 @@ int memcg_alloc_page_obj_cgroups(struct if (!vec) return -ENOMEM; - if (!set_page_objcgs(page, vec, atomic)) + memcg_data = (unsigned long) vec | MEMCG_DATA_OBJCGS; + if (new_page) { + /* + * If the slab page is brand new and nobody can yet access + * it's memcg_data, no synchronization is required and + * memcg_data can be simply assigned. + */ + page->memcg_data = memcg_data; + } else if (cmpxchg(&page->memcg_data, 0, memcg_data)) { + /* + * If the slab page is already in use, somebody can allocate + * and assign obj_cgroups in parallel. In this case the existing + * objcg vector should be reused. + */ kfree(vec); - else - kmemleak_not_leak(vec); + return 0; + } + kmemleak_not_leak(vec); return 0; } --- a/mm/slab.h~mm-memcg-slab-pre-allocate-obj_cgroups-for-slab-caches-with-slab_account-v2 +++ a/mm/slab.h @@ -240,7 +240,7 @@ static inline bool kmem_cache_debug_flag #ifdef CONFIG_MEMCG_KMEM int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, - gfp_t gfp, bool atomic); + gfp_t gfp, bool new_page); static inline void memcg_free_page_obj_cgroups(struct page *page) { @@ -308,7 +308,7 @@ static inline void memcg_slab_post_alloc if (!page_objcgs(page) && memcg_alloc_page_obj_cgroups(page, s, flags, - true)) { + false)) { obj_cgroup_uncharge(objcg, obj_full_size(s)); continue; } @@ -373,7 +373,7 @@ static inline struct mem_cgroup *memcg_f static inline int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, gfp_t gfp, - bool atomic) + bool new_page) { return 0; } @@ -418,7 +418,7 @@ static __always_inline void account_slab gfp_t gfp) { if (memcg_kmem_enabled() && (s->flags & SLAB_ACCOUNT)) - memcg_alloc_page_obj_cgroups(page, s, gfp, false); + memcg_alloc_page_obj_cgroups(page, s, gfp, true); mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s), PAGE_SIZE << order); _