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Sun, 22 Mar 2020 16:37:42 +0000 Date: Sun, 22 Mar 2020 09:37:38 -0700 From: Roman Gushchin To: Andrew Morton CC: Johannes Weiner , Michal Hocko , , , , Bharata B Rao , Subject: Re: [PATCH] mm: fork: fix kernel_stack memcg stats for various stack implementations Message-ID: <20200322163738.GA3898@carbon.dhcp.thefacebook.com> References: <20200303233550.251375-1-guro@fb.com> <20200321164856.be68344b7fac84b759e23727@linux-foundation.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200321164856.be68344b7fac84b759e23727@linux-foundation.org> X-ClientProxiedBy: CO2PR04CA0129.namprd04.prod.outlook.com (2603:10b6:104:7::31) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:400::5:5fb3) by CO2PR04CA0129.namprd04.prod.outlook.com (2603:10b6:104:7::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2835.20 via Frontend Transport; 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X-Microsoft-Antispam-Message-Info: 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 X-MS-Exchange-AntiSpam-MessageData: n1lmOpGvPv5RTHlP5Cbods4zXDkR/HWktpfcIApVMexyFJ4DJYrvqbqYIygoAcuRMrnEptqG68FiuXcmD/G0w8STVSS6mxels5L2mqI876ihUKjpbA//WL+xZiCKy+Z8Fy3VD46uPYCTuZ51hCYj1FWXdEp5+v4l33Ji0pE4FQDw5kps3NxjzzMczf4ZcF3y X-MS-Exchange-CrossTenant-Network-Message-Id: d440943b-8112-4e15-047d-08d7ce7f57b7 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Mar 2020 16:37:42.7562 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: JRhToz9oHrkjb+psW6V8ylEWrd2nbt8c7vGAZ7klztv0lvjcXIYuUR1Wg1q/NGpd X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2389 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-22_05:2020-03-21,2020-03-22 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=2 priorityscore=1501 lowpriorityscore=0 malwarescore=0 bulkscore=0 mlxscore=0 phishscore=0 impostorscore=0 clxscore=1015 mlxlogscore=999 adultscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003220099 X-FB-Internal: deliver 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 Sat, Mar 21, 2020 at 04:48:56PM -0700, Andrew Morton wrote: > On Tue, 3 Mar 2020 15:35:50 -0800 Roman Gushchin wrote: > > > Depending on CONFIG_VMAP_STACK and the THREAD_SIZE / PAGE_SIZE ratio > > the space for task stacks can be allocated using __vmalloc_node_range(), > > alloc_pages_node() and kmem_cache_alloc_node(). In the first and the > > second cases page->mem_cgroup pointer is set, but in the third it's > > not: memcg membership of a slab page should be determined using the > > memcg_from_slab_page() function, which looks at > > page->slab_cache->memcg_params.memcg . In this case, using > > mod_memcg_page_state() (as in account_kernel_stack()) is incorrect: > > page->mem_cgroup pointer is NULL even for pages charged to a non-root > > memory cgroup. > > > > It can lead to kernel_stack per-memcg counters permanently showing 0 > > on some architectures (depending on the configuration). > > > > In order to fix it, let's introduce a mod_memcg_obj_state() helper, > > which takes a pointer to a kernel object as a first argument, uses > > mem_cgroup_from_obj() to get a RCU-protected memcg pointer and > > calls mod_memcg_state(). It allows to handle all possible > > configurations (CONFIG_VMAP_STACK and various THREAD_SIZE/PAGE_SIZE > > values) without spilling any memcg/kmem specifics into fork.c . > > > > Note: this patch has been first posted as a part of the new slab > > controller patchset. This is a slightly updated version: the fixes > > tag has been added and the commit log was extended by the advice > > of Johannes Weiner. Because it's a fix that makes sense by itself, > > I'm re-posting it as a standalone patch. > > Actually, it isn't a standalone patch. It's true. I only meant it doesn't have to be a part of the slab accounting rework patchset. > > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -776,6 +776,17 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val) > > rcu_read_unlock(); > > } > > > > +void mod_memcg_obj_state(void *p, int idx, int val) > > +{ > > + struct mem_cgroup *memcg; > > + > > + rcu_read_lock(); > > + memcg = mem_cgroup_from_obj(p); > > + if (memcg) > > + mod_memcg_state(memcg, idx, val); > > + rcu_read_unlock(); > > +} > > mem_cgroup_from_obj() is later added by > http://lkml.kernel.org/r/20200117203609.3146239-1-guro@fb.com > > We could merge both mm-memcg-slab-introduce-mem_cgroup_from_obj.patch > and this patch, but that's a whole lot of stuff to backport into > -stable. > > Are you able to come up with a simpler suitable-for-stable fix? I'll try. Thank you!