From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id B9C0F6B000A for ; Thu, 28 Jun 2018 15:21:40 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id 76-v6so4569166wmw.3 for ; Thu, 28 Jun 2018 12:21:40 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id x14-v6sor3680014wrq.66.2018.06.28.12.21.39 for (Google Transport Security); Thu, 28 Jun 2018 12:21:39 -0700 (PDT) MIME-Version: 1.0 References: <20180627191250.209150-1-shakeelb@google.com> <20180627191250.209150-2-shakeelb@google.com> <20180628100253.jscxkw2d6vfhnbo5@quack2.suse.cz> In-Reply-To: <20180628100253.jscxkw2d6vfhnbo5@quack2.suse.cz> From: Shakeel Butt Date: Thu, 28 Jun 2018 12:21:26 -0700 Message-ID: Subject: Re: [PATCH 1/2] fs: fsnotify: account fsnotify metadata to kmemcg Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Andrew Morton , Michal Hocko , Johannes Weiner , Vladimir Davydov , Jan Kara , Greg Thelen , Amir Goldstein , Roman Gushchin , Alexander Viro , LKML , Cgroups , linux-fsdevel , Linux MM 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. However if you think otherwise, I will replace __GFP_ACCOUNT with SLAB_ACCOUNT. thanks, Shakeel