From: Johannes Weiner <hannes@cmpxchg.org>
To: Balbir Singh <bsingharora@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Michal Hocko <mhocko@suse.cz>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch 4/8] mm: memcg: lookup_page_cgroup (almost) never returns NULL
Date: Mon, 28 Nov 2011 10:17:03 +0100 [thread overview]
Message-ID: <20111128091703.GB9356@cmpxchg.org> (raw)
In-Reply-To: <CAKTCnz=CObdw0z4Qf36=afwwApuTer5C4Jp21QUko-H__q-+aA@mail.gmail.com>
On Mon, Nov 28, 2011 at 12:33:31PM +0530, Balbir Singh wrote:
> On Wed, Nov 23, 2011 at 9:12 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> > From: Johannes Weiner <jweiner@redhat.com>
> >
> > Pages have their corresponding page_cgroup descriptors set up before
> > they are used in userspace, and thus managed by a memory cgroup.
> >
> > The only time where lookup_page_cgroup() can return NULL is in the
> > page sanity checking code that executes while feeding pages into the
> > page allocator for the first time.
> >
>
> This is a legacy check from the days when we allocated PC during fault
> time on demand. It might make sense to assert on !pc in DEBUG_VM mode
> at some point in the future
I don't think a BUG_ON bears more information than a null-pointer
dereference.
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next prev parent reply other threads:[~2011-11-28 9:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-23 15:42 [patch 0/8] mm: memcg fixlets for 3.3 Johannes Weiner
2011-11-23 15:42 ` [patch 1/8] mm: oom_kill: remove memcg argument from oom_kill_task() Johannes Weiner
2011-11-23 22:35 ` David Rientjes
2011-11-23 23:57 ` KAMEZAWA Hiroyuki
2011-11-24 9:07 ` Michal Hocko
2011-11-28 0:37 ` Balbir Singh
2011-11-23 15:42 ` [patch 2/8] mm: unify remaining mem_cont, mem, etc. variable names to memcg Johannes Weiner
2011-11-23 22:40 ` David Rientjes
2011-11-23 23:58 ` KAMEZAWA Hiroyuki
2011-11-24 9:17 ` Michal Hocko
2011-11-28 0:42 ` Balbir Singh
2011-11-23 15:42 ` [patch 3/8] mm: memcg: clean up fault accounting Johannes Weiner
2011-11-24 0:00 ` KAMEZAWA Hiroyuki
2011-11-24 9:33 ` Michal Hocko
2011-11-24 9:51 ` Johannes Weiner
2011-11-28 0:45 ` Balbir Singh
2011-11-23 15:42 ` [patch 4/8] mm: memcg: lookup_page_cgroup (almost) never returns NULL Johannes Weiner
2011-11-24 0:01 ` KAMEZAWA Hiroyuki
2011-11-24 9:52 ` Michal Hocko
2011-11-24 10:05 ` Johannes Weiner
2011-11-24 10:26 ` Michal Hocko
2011-11-28 9:15 ` Johannes Weiner
2011-11-28 9:34 ` Johannes Weiner
2011-11-28 10:12 ` Michal Hocko
2011-11-28 7:03 ` Balbir Singh
2011-11-28 9:17 ` Johannes Weiner [this message]
2011-11-23 15:42 ` [patch 5/8] mm: memcg: remove unneeded checks from newpage_charge() Johannes Weiner
2011-11-24 0:04 ` KAMEZAWA Hiroyuki
2011-11-24 9:04 ` Johannes Weiner
2011-11-24 10:30 ` Michal Hocko
2011-11-24 11:58 ` Johannes Weiner
2011-11-23 15:42 ` [patch 6/8] mm: memcg: remove unneeded checks from uncharge_page() Johannes Weiner
2011-11-24 0:06 ` KAMEZAWA Hiroyuki
2011-11-24 9:06 ` Johannes Weiner
2011-11-24 10:34 ` Michal Hocko
2011-11-23 15:42 ` [patch 7/8] mm: memcg: modify PageCgroupAcctLRU non-atomically Johannes Weiner
2011-11-23 18:52 ` Hugh Dickins
2011-11-24 8:53 ` Johannes Weiner
2011-11-24 0:09 ` KAMEZAWA Hiroyuki
2011-11-24 8:55 ` Johannes Weiner
2011-11-23 15:42 ` [patch 8/8] mm: memcg: modify PageCgroupCache non-atomically Johannes Weiner
2011-11-24 0:13 ` KAMEZAWA Hiroyuki
2011-11-24 9:13 ` Johannes Weiner
2011-11-24 6:09 ` [patch 0/8] mm: memcg fixlets for 3.3 Balbir Singh
2011-11-24 9:45 ` Johannes Weiner
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