Messages in this thread | | | Date | Fri, 12 Jun 2009 07:55:44 +0900 | Subject | Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2 | From | Minchan Kim <> |
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2009/6/11 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>: > Minchan Kim wrote: >> 2009/6/11 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>: >>> Minchan Kim さん wrote: >>>> On Thu, Jun 11, 2009 at 5:38 PM, KAMEZAWA >>>> Hiroyuki<kamezawa.hiroyu@jp.fujitsu.com> wrote: >>>>> How about this ? >>>>> >>>>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> >>>>> >>>>> Lumpy reclaim check pages from their pfn. Then, it can find >>>>> unevictable >>>>> pages >>>>> in its loop. >>>>> Abort lumpy reclaim when we find Unevictable page, we never get a lump >>>>> of pages for requested order. >>>>> >>>>> Changelog: v1->v2 >>>>> ?- rewrote commet. >>>>> >>>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> >>>>> --- >>>>> ?mm/vmscan.c | ? ?9 +++++++++ >>>>> ?1 file changed, 9 insertions(+) >>>>> >>>>> Index: lumpy-reclaim-trial/mm/vmscan.c >>>>> =================================================================== >>>>> --- lumpy-reclaim-trial.orig/mm/vmscan.c >>>>> +++ lumpy-reclaim-trial/mm/vmscan.c >>>>> @@ -936,6 +936,15 @@ static unsigned long isolate_lru_pages(u >>>>> ? ? ? ? ? ? ? ? ? ? ? ?/* Check that we have not crossed a zone >>>>> boundary. */ >>>>> ? ? ? ? ? ? ? ? ? ? ? ?if (unlikely(page_zone_id(cursor_page) != >>>>> zone_id)) >>>>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?continue; >>>>> + ? ? ? ? ? ? ? ? ? ? ? /* >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* We tries to free all pages in this range to >>>>> create >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* a free large page. Then, if the range >>>>> includes a page >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* never be reclaimed, we have no reason to do >>>>> more. >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* PageUnevictable page is not a page which >>>>> can >>>>> be >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* easily freed. Abort this scan now. >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?*/ >>>>> + ? ? ? ? ? ? ? ? ? ? ? if (unlikely(PageUnevictable(cursor_page))) >>>>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break; >>>> >>>> __isolate_lru_pages already checked PageUnevictable to return error. >>>> I want to remove repeated check although it is trivial. >>>> >>>> By your patch, It seems to remove PageUnevictable check in >>>> __isolate_lru_pages. >>>> >>> yes. >>> >>>> But I know that. If we remove PageUnevictable check in >>>> __isolate_lru_pages, it can't go into BUG in non-lumpy case. ( I >>>> mentioned following as code) >>>> >>> In non-lumpy case, we'll never see Unevictable, maybe. >> >> I think so if it doesn't happen RAM failure. >> AFAIK, Unevictable check didn't related with RAM failure. >> >>> >>>> ? ? ? ? ? ? ? ? case -EBUSY: >>>> ? ? ? ? ? ? ? ? ? ? ? ? /* else it is being freed elsewhere */ >>>> ? ? ? ? ? ? ? ? ? ? ? ? list_move(&page->lru, src); >>>> ? ? ? ? ? ? ? ? ? ? ? ? continue; >>>> >>>> ? ? ? ? ? ? ? ? default: >>>> ? ? ? ? ? ? ? ? ? ? ? ? BUG(); >>>> ? ? ? ? ? ? ? ? } >>>> >>>> >>>> It means we can remove BUG in non-lumpy case and then add BUG into >>>> __isolate_lru_pages directly. >>>> >>>> If we can do it, we can remove unnecessary PageUnevictable check in >>>> __isolate_lru_page. >>>> >>> Hmm, but Unevicable check had tons of troubles at its implementation >>> and I don't want to do it at once. >> >> I think it's not a big problem. >> As comment said, the check's goal is to prevent in lumpy case. >> /* >> * When this function is being called for lumpy reclaim, we >> * initially look into all LRU pages, active, inactive and >> * unevictable; only give shrink_page_list evictable pages. >> */ >> if (PageUnevictable(page)) >> return ret; >> >> So I think we can remove this check. >> > agreed. > >>>> I am not sure this is right in case of memcg. >>>> >>> I think we don't see Unevictable in memcg's path if my memcg-lru code >>> works as designed. >>> >>> I'll postpone this patch for a while until my brain works well. >> >> If you have a concern about that, how about this ? >> (This code will be hunk since gmail webserver always mangle. Pz,forgive >> me) >> Also, we can CC original authors. >> > I'll schedule this optimization/clean up for unevictable case in queue. > Thank you for inputs. > > But it's now merge-window, I'd like to push bugfix first.(1/3 and 3/3)
I agree. It's more important now.
> I'd like to scheule Unevictable case fix after rc1(when mmotm stack seems > to be pushed out to Linus.) > And I'll add > int __isolate_lru_page(...) > { > VM_BUG_ON(PageUnevictable(page)); > } > as sanity check for mmotm test time. > > Thank you for all your help.
I also thanks you for considering my comment.
You may add my review sign. :) Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
> -Kame > >
-- Kinds regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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