On Fri, 22 Jul 2011 13:20:25 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > percpu_charge_mutex protects from multiple simultaneous per-cpu charge > caches draining because we might end up having too many work items. > At least this was the case until 26fe6168 (memcg: fix percpu cached > charge draining frequency) when we introduced a more targeted draining > for async mode. > Now that also sync draining is targeted we can safely remove mutex > because we will not send more work than the current number of CPUs. > FLUSHING_CACHED_CHARGE protects from sending the same work multiple > times and stock->nr_pages == 0 protects from pointless sending a work > if there is obviously nothing to be done. This is of course racy but we > can live with it as the race window is really small (we would have to > see FLUSHING_CACHED_CHARGE cleared while nr_pages would be still > non-zero). > The only remaining place where we can race is synchronous mode when we > rely on FLUSHING_CACHED_CHARGE test which might have been set by other > drainer on the same group but we should wait in that case as well. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> -- 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>