From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id BE37B6B0007 for ; Fri, 29 Jun 2018 05:52:05 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id c20-v6so2813879eds.21 for ; Fri, 29 Jun 2018 02:52:05 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o61-v6si4279822edd.177.2018.06.29.02.52.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Jun 2018 02:52:04 -0700 (PDT) Date: Fri, 29 Jun 2018 11:52:00 +0200 From: Michal Hocko Subject: Re: [PATCH 1/2] fs: fsnotify: account fsnotify metadata to kmemcg Message-ID: <20180629095200.GF13860@dhcp22.suse.cz> References: <20180627191250.209150-1-shakeelb@google.com> <20180627191250.209150-2-shakeelb@google.com> <20180628100253.jscxkw2d6vfhnbo5@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Shakeel Butt Cc: Jan Kara , Andrew Morton , Johannes Weiner , Vladimir Davydov , Jan Kara , Greg Thelen , Amir Goldstein , Roman Gushchin , Alexander Viro , LKML , Cgroups , linux-fsdevel , Linux MM On Thu 28-06-18 12:21:26, Shakeel Butt wrote: > On Thu, Jun 28, 2018 at 12:03 PM Jan Kara wrote: > > > > On Wed 27-06-18 12:12:49, Shakeel Butt wrote: > > > A lot of memory can be consumed by the events generated for the huge or > > > unlimited queues if there is either no or slow listener. This can cause > > > system level memory pressure or OOMs. So, it's better to account the > > > fsnotify kmem caches to the memcg of the listener. > > > > > > However the listener can be in a different memcg than the memcg of the > > > producer and these allocations happen in the context of the event > > > producer. This patch introduces remote memcg charging API which the > > > producer can use to charge the allocations to the memcg of the listener. > > > > > > There are seven fsnotify kmem caches and among them allocations from > > > dnotify_struct_cache, dnotify_mark_cache, fanotify_mark_cache and > > > inotify_inode_mark_cachep happens in the context of syscall from the > > > listener. So, SLAB_ACCOUNT is enough for these caches. > > > > > > The objects from fsnotify_mark_connector_cachep are not accounted as they > > > are small compared to the notification mark or events and it is unclear > > > whom to account connector to since it is shared by all events attached to > > > the inode. > > > > > > The allocations from the event caches happen in the context of the event > > > producer. For such caches we will need to remote charge the allocations > > > to the listener's memcg. Thus we save the memcg reference in the > > > fsnotify_group structure of the listener. > > > > > > This patch has also moved the members of fsnotify_group to keep the size > > > same, at least for 64 bit build, even with additional member by filling > > > the holes. > > > > ... > > > > > static int __init fanotify_user_setup(void) > > > { > > > - fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC); > > > + fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, > > > + SLAB_PANIC|SLAB_ACCOUNT); > > > fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC); > > > if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) { > > > fanotify_perm_event_cachep = > > > > Why don't you setup also fanotify_event_cachep and > > fanotify_perm_event_cachep caches with SLAB_ACCOUNT and instead specify > > __GFP_ACCOUNT manually? Otherwise the patch looks good to me. > > > > Hi Jan, IMHO having a visible __GFP_ACCOUNT along with > memalloc_use_memcg() makes the code more explicit and readable that we > want to targeted/remote memcg charging. Agreed. If you had an implicit SLAB_ACCOUNT then you could get inconsistencies when some allocations would get charged to the current task while others would not. -- Michal Hocko SUSE Labs