Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 1/5] vmscan: remove all_unreclaimable check from direct reclaim path completely | Date | Thu, 24 Mar 2011 15:16:25 +0900 (JST) |
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Hi
> Thanks for your effort, Kosaki. > But I still doubt this patch is good. > > This patch makes early oom killing in hibernation as it skip > all_unreclaimable check. > Normally, hibernation needs many memory so page_reclaim pressure > would be big in small memory system. So I don't like early give up.
Wait. When occur big pressure? hibernation reclaim pressure (sc->nr_to_recliam) depend on physical memory size. therefore a pressure seems to don't depend on the size.
> Do you think my patch has a problem? Personally, I think it's very > simple and clear. :)
To be honest, I dislike following parts. It's madness on madness.
static bool zone_reclaimable(struct zone *zone) { if (zone->all_unreclaimable) return false; return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; }
The function require a reviewer know
o pages_scanned and all_unreclaimable are racy o at hibernation, zone->all_unreclaimable can be false negative, but can't be false positive.
And, a function comment of all_unreclaimable() says
/* * As hibernation is going on, kswapd is freezed so that it can't mark * the zone into all_unreclaimable. It can't handle OOM during hibernation. * So let's check zone's unreclaimable in direct reclaim as well as kswapd. */
But, now it is no longer copy of kswapd algorithm.
If you strongly prefer this idea even if you hear above explanation, please consider to add much and much comments. I can't say current your patch is enough readable/reviewable.
Thanks.
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