Messages in this thread | | | Date | Thu, 10 Mar 2011 15:58:29 +0900 | Subject | Re: [PATCH] mm: check zone->all_unreclaimable in all_unreclaimable() | From | Minchan Kim <> |
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Hi Kame,
Sorry for late response. I had a time to test this issue shortly because these day I am very busy. This issue was interesting to me. So I hope taking a time for enough testing when I have a time. I should find out root cause of livelock.
I will answer your comment after it. :) Thanks!
On Wed, Mar 9, 2011 at 2:37 PM, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Tue, 8 Mar 2011 08:45:51 +0900 > Minchan Kim <minchan.kim@gmail.com> wrote: > >> On Tue, Mar 8, 2011 at 6:58 AM, Andrew Morton <akpm@linux-foundation.org> wrote: >> > On Sun, 6 Mar 2011 02:07:59 +0900 >> > Minchan Kim <minchan.kim@gmail.com> wrote: >> > Any alternative proposals? We should get the livelock fixed if possible.. >> > >> >> And we should avoid unnecessary OOM kill if possible. >> >> I think the problem is caused by (zone->pages_scanned < >> zone_reclaimable_pages(zone) * 6). I am not sure (* 6) is a best. It >> would be rather big on recent big DRAM machines. >> > > It means 3 times full-scan from the highest priority to the lowest > and cannot freed any pages. I think big memory machine tend to have > more cpus, so don't think it's big. > >> I think it is a trade-off between latency and OOM kill. >> If we decrease the magic value, maybe we should prevent the almost >> livelock but happens unnecessary OOM kill. >> > > Hmm, should I support a sacrifice feature 'some signal(SIGINT?) will be sent by > the kernel when it detects system memory is in short' in cgroup ? > (For example, if full LRU scan is done in a zone, notifier > works and SIGINT will be sent.) > >> And I think zone_reclaimable not fair. >> For example, too many scanning makes reclaimable state to >> unreclaimable state. Maybe it takes a very long time. But just some >> page free makes unreclaimable state to reclaimabe with very easy. So >> we need much painful reclaiming for changing reclaimable state with >> unreclaimabe state. it would affect latency very much. >> >> Maybe we need more smart zone_reclaimabe which is adaptive with memory pressure. >> > I agree. > > Thanks, > -Kame > >
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