Hi Sergey, On Fri, Jul 10, 2015 at 10:58:28AM +0900, Sergey Senozhatsky wrote: > On (07/10/15 10:32), Minchan Kim wrote: > > There is no reason to prevent select ZS_ALMOST_FULL as migration > > source if we cannot find source from ZS_ALMOST_EMPTY. > > > > With this patch, zs_can_compact will return more exact result. > > > > wouldn't that be too aggresive? > > drainig 'only ZS_ALMOST_EMPTY classes' sounds safer than draining > 'ZS_ALMOST_EMPTY and ZS_ALMOST_FULL clases'. you seemed to be worried > that compaction can leave no unused objects in classes, which will > result in zspage allocation happening right after compaction. it looks > like here the chances to cause zspage allocation are even higher. don't > you think so?
Good question. My worry was failure of order-0 page allocation in zram-swap path when memory presssure is really heavy but I didn't insist to you from sometime. The reason I changed my mind was 1. It's almost dead system if there is no order-0 page 2. If old might be working well, it's not our design, just luck. > > > Signed-off-by: Minchan Kim <[email protected]> > > --- > > mm/zsmalloc.c | 19 ++++++++++++------- > > 1 file changed, 12 insertions(+), 7 deletions(-) > > > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > > index 8c78bcb..7bd7dde 100644 > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -1687,12 +1687,20 @@ static enum fullness_group putback_zspage(struct > > zs_pool *pool, > > static struct page *isolate_source_page(struct size_class *class) > > { > > struct page *page; > > + int i; > > + bool found = false; > > > > - page = class->fullness_list[ZS_ALMOST_EMPTY]; > > - if (page) > > - remove_zspage(page, class, ZS_ALMOST_EMPTY); > > + for (i = ZS_ALMOST_EMPTY; i >= ZS_ALMOST_FULL; i--) { > > + page = class->fullness_list[i]; > > + if (!page) > > + continue; > > > > - return page; > > + remove_zspage(page, class, i); > > + found = true; > > + break; > > + } > > + > > + return found ? page : NULL; > > } > > > > /* > > @@ -1706,9 +1714,6 @@ static unsigned long zs_can_compact(struct size_class > > *class) > > { > > unsigned long obj_wasted; > > > > - if (!zs_stat_get(class, CLASS_ALMOST_EMPTY)) > > - return 0; > > - > > well, you asked to add this check like a week or two ago (it's not even > in -next yet) and now you remove it. The reason I wanted to check CLASS_ALMOST_EMPTY is to make zs_can_compact exact. But with this patch, we can achieve it without above. > > > obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) - > > zs_stat_get(class, OBJ_USED); > > > > -ss -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
