On Thu, 12 May 2011 23:25:00 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 13 May 2011 12:10:30 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > ZONE_CONGESTED should be a state of global memory reclaim. > > If not, a busy memcg sets this and give unnecessary throttoling in > > wait_iff_congested() against memory recalim in other contexts. This makes > > system performance bad. > > > > I'll think about "memcg is congested!" flag is required or not, later. > > But this fix is required 1st. > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > --- > > mm/vmscan.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > Index: mmotm-May11/mm/vmscan.c > > =================================================================== > > --- mmotm-May11.orig/mm/vmscan.c > > +++ mmotm-May11/mm/vmscan.c > > @@ -941,7 +941,8 @@ keep_lumpy: > > * back off and wait for congestion to clear because further reclaim > > * will encounter the same problem > > */ > > - if (nr_dirty == nr_congested && nr_dirty != 0) > > + if (scanning_global_lru(sc) && > > + nr_dirty == nr_congested && nr_dirty != 0) > > zone_set_flag(zone, ZONE_CONGESTED); > > > > nit: which is more probable? nr_dirty==nr_congested or > scanning_global_lru(sc)? > > If the user is actually _using_ memcg then > If the user uses memcg, yes, nr_dirty == nr_congested is more probable. If user doesn't, scanning_global_lru() returns always true. > --- a/mm/vmscan.c~a > +++ a/mm/vmscan.c > @@ -937,7 +937,7 @@ keep_lumpy: > * back off and wait for congestion to clear because further reclaim > * will encounter the same problem > */ > - if (nr_dirty == nr_congested && nr_dirty != 0) > + if (nr_dirty == nr_congested && scanning_global_lru(sc) && nr_dirty) > zone_set_flag(zone, ZONE_CONGESTED); > > free_page_list(&free_pages); > > > is more efficient. If the user isn't using memcg then your patch is faster? > Hmm, maybe your fix is always faster. But in many case, if nr_congested == nr_dirty, nr_dirty == 0 because vmscan just finds clean pages...fast path. So, nr_dirty should be 1st ? How about this ? == ZONE_CONGESTED should be a state of global memory reclaim. Changelog:v1->v2 - fixed the order of conditions. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: mmotm-May11/mm/vmscan.c =================================================================== --- mmotm-May11.orig/mm/vmscan.c +++ mmotm-May11/mm/vmscan.c @@ -941,7 +941,7 @@ keep_lumpy: * back off and wait for congestion to clear because further reclaim * will encounter the same problem */ - if (nr_dirty == nr_congested && nr_dirty != 0) + if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) zone_set_flag(zone, ZONE_CONGESTED); free_page_list(&free_pages); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>