On Mon, Feb 13, 2012 at 7:07 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> From 9cdb3b63dc8d08cc2220c54c80438c13433a0d12 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> 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()
I assume that CPU-A will take heavy lock after synchronize_rcu() when
updating variables read by CPU-B.
> memcontrol.c | 65 ++++++++++++++++++++++-------------------------------------
> 1 file changed, 25 insertions(+), 40 deletions(-)
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Greg Thelen <gthelen@xxxxxxxxxx>
> ---
> mm/memcontrol.c | 70 +++++++++++++++++++++++-------------------------------
> 1 files changed, 30 insertions(+), 40 deletions(-)
> @@ -2089,11 +2082,8 @@ static int __cpuinit memcg_cpu_hotplug_callback(struct notifier_block *nb,
> struct memcg_stock_pcp *stock;
> struct mem_cgroup *iter;
>
> - if ((action == CPU_ONLINE)) {
> - for_each_mem_cgroup(iter)
> - synchronize_mem_cgroup_on_move(iter, cpu);
> + if ((action == CPU_ONLINE))
Extra parenthesis. I recommend:
+ if (action == CPU_ONLINE)
--
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