From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754667AbdBGRKK (ORCPT ); Tue, 7 Feb 2017 12:10:10 -0500 Received: from mail-yw0-f193.google.com ([209.85.161.193]:33299 "EHLO mail-yw0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753651AbdBGRKI (ORCPT ); Tue, 7 Feb 2017 12:10:08 -0500 Date: Tue, 7 Feb 2017 12:10:06 -0500 From: Tejun Heo To: Andrew Morton Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vladimir Davydov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, Michal Hocko , kernel-team@fb.com Subject: Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional Message-ID: <20170207171006.GB6164@htj.duckdns.org> References: <20170204145203.GB26958@mtj.duckdns.org> <20170206162213.30f909b5ce4c681e2217fb4f@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170206162213.30f909b5ce4c681e2217fb4f@linux-foundation.org> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Andrew. On Mon, Feb 06, 2017 at 04:22:13PM -0800, Andrew Morton wrote: > > #ifdef CONFIG_MEMCG > > - if (is_root_cache(s)) { > > + if (is_root_cache(s) && memcg_sysfs_enabled) { > > This could be turned on and off after bootup but I guess the result > could be pretty confusing. > > However there would be useful use cases? The user would normally have > this disabled but if he wants to do a bit of debugging then turn this > on, create a memcg, have a poke around then turn the feature off again. Hmm... maybe. It's somewhat nasty to do after-the-fact. You would have to re-walk all the caches to create and destroy the sysfs entries. Given that it's a pretty fringe debug feature, I'm not sure the added complexity would be justified. > > s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj); > > if (!s->memcg_kset) { > > err = -ENOMEM; > > @@ -5673,7 +5695,8 @@ static void sysfs_slab_remove(struct kme > > return; > > > > #ifdef CONFIG_MEMCG > > - kset_unregister(s->memcg_kset); > > + if (s->memcg_kset) > > + kset_unregister(s->memcg_kset); > > kset_unregister(NULL) is legal > > --- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix > +++ a/mm/slub.c > @@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme > return; > > #ifdef CONFIG_MEMCG > - if (s->memcg_kset) > - kset_unregister(s->memcg_kset); > + kset_unregister(s->memcg_kset); > #endif > kobject_uevent(&s->kobj, KOBJ_REMOVE); > kobject_del(&s->kobj); Ah, of course, looks good to me. Thanks. -- tejun