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>,
Michal Hocko <mhocko@suse.cz>, Hugh Dickins <hughd@google.com>,
Greg Thelen <gthelen@google.com>, Ying Han <yinghan@google.com>
Subject: Re: [PATCH 2/6] memcg: simplify move_account() check.
Date: Mon, 20 Feb 2012 09:55:21 +0100 [thread overview]
Message-ID: <20120220085521.GB1677@cmpxchg.org> (raw)
In-Reply-To: <20120217182612.810f6784.kamezawa.hiroyu@jp.fujitsu.com>
On Fri, Feb 17, 2012 at 06:26:12PM +0900, KAMEZAWA Hiroyuki wrote:
> >From 3b6620772d7fd7b2126d5253eafb6afaf4ed6e34 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 2 Feb 2012 10:02:39 +0900
> Subject: [PATCH 2/6] memcg: simplify move_account() check.
>
> In memcg, for avoiding take-lock-irq-off at accessing page_cgroup,
> a logic, flag + rcu_read_lock(), is used. This works as following
>
> CPU-A CPU-B
> rcu_read_lock()
> set flag
> if(flag is set)
> take heavy lock
> do job.
> synchronize_rcu() rcu_read_unlock()
> take heavy lock.
>
> In recent discussion, it's argued that using per-cpu value for this
> flag just complicates the code because 'set flag' is very rare.
>
> This patch changes 'flag' implementation from percpu to atomic_t.
> This will be much simpler.
>
> Changelog v5.
> - removed redundant ().
> - updated patch description.
>
> Changelog: v4
> - fixed many typos.
> - fixed return value to be bool
> - add comments.
> Changelog: v3
> - this is a new patch since v3.
>
> Acked-by: Greg Thelen <gthelen@google.com>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Much better!
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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next prev parent reply other threads:[~2012-02-20 8:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-17 9:24 [PATCH 0/6] page cgroup diet v5 KAMEZAWA Hiroyuki
2012-02-17 9:25 ` [PATCH 1/6] memcg: remove EXPORT_SYMBOL(mem_cgroup_update_page_stat) KAMEZAWA Hiroyuki
2012-02-20 8:54 ` Johannes Weiner
2012-02-17 9:26 ` [PATCH 2/6] memcg: simplify move_account() check KAMEZAWA Hiroyuki
2012-02-20 8:55 ` Johannes Weiner [this message]
2012-02-17 9:26 ` [PATCH 3/6] memcg: remove PCG_MOVE_LOCK flag from page_cgroup KAMEZAWA Hiroyuki
2012-02-20 8:56 ` Johannes Weiner
2012-02-17 9:27 ` [PATCH 4/6] memcg: use new logic for page stat accounting KAMEZAWA Hiroyuki
2012-02-28 12:22 ` Johannes Weiner
2012-02-17 9:28 ` [PATCH 5/6] memcg: remove PCG_FILE_MAPPED KAMEZAWA Hiroyuki
2012-02-18 13:39 ` Johannes Weiner
2012-02-18 14:43 ` Hillf Danton
2012-02-19 23:52 ` KAMEZAWA Hiroyuki
2012-02-17 9:28 ` [PATCH 6/6] memcg: fix performance of mem_cgroup_begin_update_page_stat() KAMEZAWA Hiroyuki
2012-02-28 12:25 ` Johannes Weiner
2012-02-17 10:04 ` [PATCH 0/6] page cgroup diet v5 KAMEZAWA Hiroyuki
2012-02-17 21:45 ` Andrew Morton
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