Messages in this thread |  | | | Date | Wed, 23 Mar 2011 17:24:23 +0900 | | From | Minchan Kim <> | | Subject | Re: [PATCH 1/5] vmscan: remove all_unreclaimable check from direct reclaim path completely |
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On Wed, Mar 23, 2011 at 04:13:21PM +0900, KOSAKI Motohiro wrote: > > Okay. I got it. > > > > The problem is following as. > > By the race the free_pcppages_bulk and balance_pgdat, it is possible > > zone->all_unreclaimable = 1 and zone->pages_scanned = 0. > > DMA zone have few LRU pages and in case of no-swap and big memory > > pressure, there could be a just a page in inactive file list like your > > example. (anon lru pages isn't important in case of non-swap system) > > In such case, shrink_zones doesn't scan the page at all until priority > > become 0 as get_scan_count does scan >>= priority(it's mostly zero). > > Nope. > > if (zone->all_unreclaimable && priority != DEF_PRIORITY) > continue; > > This tow lines mean, all_unreclaimable prevent priority 0 reclaim. >
Yes. I missed it. Thanks.
> > > And although priority become 0, nr_scan_try_batch returns zero until > > saved pages become 32. So for scanning the page, at least, we need 32 > > times iteration of priority 12..0. If system has fork-bomb, it is > > almost livelock. > > Therefore, 1000 times get_scan_count(DEF_PRIORITY) takes 1000 times no-op. > > > > > If is is right, how about this? > > Boo. > You seems forgot why you introduced current all_unreclaimable() function. > While hibernation, we can't trust all_unreclaimable.
Hmm. AFAIR, the why we add all_unreclaimable is when the hibernation is going on, kswapd is freezed so it can't mark the zone->all_unreclaimable. So I think hibernation can't be a problem. Am I miss something?
-- Kind regards, Minchan Kim
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