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@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() > 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@xxxxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Much better! Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>