Messages in this thread Patch in this message | | | Date | Thu, 11 Jun 2009 20:59:28 +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 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.
>> 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.
--- a/mm/vmscan.c ++ b/mm/vmscan.c @@ -936,19 +936,20 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, /* Check that we have not crossed a zone boundary. */ if (unlikely(page_zone_id(cursor_page) != zone_id)) continue; - switch (__isolate_lru_page(cursor_page, mode, file)) { - case 0: + if (__isolate_lru_page(cursor_page, mode, file) == 0) { list_move(&cursor_page->lru, dst); nr_taken++; scan++; - break; - - case -EBUSY: - /* else it is being freed elsewhere */ - list_move(&cursor_page->lru, src); - default: - break; /* ! on LRU or wrong list */ } + else if (PageUnevictable(cursor_page)) + /* + * 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. + */ + break } }
> Thanks, > -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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