From: Johannes Weiner <hannes@cmpxchg.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"nishimura@mxp.nes.nec.co.jp" <nishimura@mxp.nes.nec.co.jp>,
"balbir@linux.vnet.ibm.com" <balbir@linux.vnet.ibm.com>
Subject: Re: [PATCH 2/4] memcg: fix USED bit handling at uncharge in THP
Date: Wed, 19 Jan 2011 13:10:43 +0100 [thread overview]
Message-ID: <20110119121043.GB2232@cmpxchg.org> (raw)
In-Reply-To: <20110118114049.5ffdf5da.kamezawa.hiroyu@jp.fujitsu.com>
Hello KAMEZAWA-san,
On Tue, Jan 18, 2011 at 11:40:49AM +0900, KAMEZAWA Hiroyuki wrote:
> +void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail)
> +{
> + struct page_cgroup *head_pc = lookup_page_cgroup(head);
> + struct page_cgroup *tail_pc = lookup_page_cgroup(tail);
> + unsigned long flags;
> +
> + /*
> + * We have no races witch charge/uncharge but will have races with
> + * page state accounting.
> + */
> + move_lock_page_cgroup(head_pc, &flags);
> +
> + tail_pc->mem_cgroup = head_pc->mem_cgroup;
> + smp_wmb(); /* see __commit_charge() */
I thought the barriers were needed because charging does not hold the
lru lock. But here we do, and all the 'lockless' read-sides do so as
well. Am I missing something or can this barrier be removed?
Hannes
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next prev parent reply other threads:[~2011-01-19 12:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-18 2:35 [PATCH 0/4] fix THP and memcg issues v3 KAMEZAWA Hiroyuki
2011-01-18 2:36 ` [PATCH 1/4] memcg: modify accounting function for supporting THP better KAMEZAWA Hiroyuki
2011-01-18 2:40 ` [PATCH 2/4] memcg: fix USED bit handling at uncharge in THP KAMEZAWA Hiroyuki
2011-01-19 12:10 ` Johannes Weiner [this message]
2011-01-20 0:55 ` KAMEZAWA Hiroyuki
2011-01-18 2:42 ` [PATCH 3/4] memcg: fix LRU accounting with THP KAMEZAWA Hiroyuki
2011-01-18 2:43 ` [PATCH 4/4] memcg: fix rmdir, force_empty " KAMEZAWA Hiroyuki
2011-01-20 13:41 ` Johannes Weiner
2011-01-20 23:39 ` KAMEZAWA Hiroyuki
2011-01-20 23:41 ` KAMEZAWA Hiroyuki
2011-01-21 0:21 ` nishimura
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