On Mon, Jan 23, 2012 at 08:30:42PM +0800, Hillf Danton wrote: > On Mon, Jan 23, 2012 at 6:47 PM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > On Mon, Jan 23, 2012 at 09:55:07AM +0800, Hillf Danton wrote: > >> To avoid reduction in performance of reclaimee, checking overreclaim is added > >> after shrinking lru list, when pages are reclaimed from mem cgroup. > >> > >> If over reclaim occurs, shrinking remaining lru lists is skipped, and no more > >> reclaim for reclaim/compaction. > >> > >> Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx> > >> --- > >> > >> --- a/mm/vmscan.c Mon Jan 23 00:23:10 2012 > >> +++ b/mm/vmscan.c Mon Jan 23 09:57:20 2012 > >> @@ -2086,6 +2086,7 @@ static void shrink_mem_cgroup_zone(int p > >> unsigned long nr_reclaimed, nr_scanned; > >> unsigned long nr_to_reclaim = sc->nr_to_reclaim; > >> struct blk_plug plug; > >> + bool memcg_over_reclaimed = false; > >> > >> restart: > >> nr_reclaimed = 0; > >> @@ -2103,6 +2104,11 @@ restart: > >> > >> nr_reclaimed += shrink_list(lru, nr_to_scan, > >> mz, sc, priority); > >> + > >> + memcg_over_reclaimed = !scanning_global_lru(mz) > >> + && (nr_reclaimed >= nr_to_reclaim); > >> + if (memcg_over_reclaimed) > >> + goto out; > > > > Since this merge window, scanning_global_lru() is always false when > > the memory controller is enabled, i.e. most common configurations and > > distribution kernels. > > > > This will with quite likely have bad effects on zone balancing, > > pressure balancing between anon/file lru etc, while you haven't shown > > that any workloads actually benefit from this. > > > Hi Johannes > > Thanks for your comment, first. > > Impact on zone balance and lru-list balance is introduced actually, but I > dont think the patch is totally responsible for the balance mentioned, > because soft limit, embedded in mem cgroup, is setup by users according to > whatever tastes they have. > > Though there is room for the patch to be fine tuned in this direction or that, > over reclaim should not be neglected entirely, but be avoided as much as we > could, or users are enforced to set up soft limit with much care not to mess > up zone balance. Overreclaim is absolutely horrible with soft limits, but I think there are more direct reasons than checking nr_to_reclaim only after a full zone scan, for example, soft limit reclaim is invoked on zones that are totally fine. -- 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>