Messages in this thread | | | Date | Mon, 17 Nov 2008 09:13:37 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH -mm] vmscan: bail out of page reclaim after swap_cluster_max pages |
| |
KAMEZAWA Hiroyuki wrote: > On Sun, 16 Nov 2008 16:38:56 +0900 (JST) > KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote: > >> One more point. >> >>> Sometimes the VM spends the first few priority rounds rotating back >>> referenced pages and submitting IO. Once we get to a lower priority, >>> sometimes the VM ends up freeing way too many pages. >>> >>> The fix is relatively simple: in shrink_zone() we can check how many >>> pages we have already freed and break out of the loop. >>> >>> However, in order to do this we do need to know how many pages we already >>> freed, so move nr_reclaimed into scan_control. >> IIRC, Balbir-san explained the implemetation of the memcgroup >> force cache dropping feature need non bail out at the past reclaim >> throttring discussion. >>
Yes, for we used that for force_empty() in the past, but see below
>> I am not sure about this still right or not (iirc, memcgroup implemetation >> was largely changed). >> >> Balbir-san, Could you comment to this patch? >> >> > I'm not Balbir-san but there is no "force-cache-dropping" feature now. > (I have no plan to do that.) > > But, mem+swap controller will need to modify reclaim path to do "cache drop > first" becasue the amount of "mem+swap" will not change when "mem+swap" hit > limit. It's now set "sc.may_swap" to 0. >
Yes, there have been several changes to force_empty() and its meaning, including movement of accounts. Since you've made most of the recent changes, your comments are very relevant.
> Hmm, I hope memcg is a silver bullet to this kind of special? workload in > long term.
:-) From my perspective, hierarchy, soft limits (sharing memory when there is no contention), some form of over commit support and getting swappiness to work correctly are very important for memcg.
-- Balbir
| |