Messages in this thread | | | Date | Wed, 31 Oct 2012 21:41:25 +0800 | From | Jianguo Wu <> | Subject | Re: [Patch v4 3/8] memory-hotplug: fix NR_FREE_PAGES mismatch |
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On 2012/10/31 19:23, Wen Congyang wrote: > NR_FREE_PAGES will be wrong after offlining pages. We add/dec > NR_FREE_PAGES like this now: > > 1. move all pages in buddy system to MIGRATE_ISOLATE, and dec NR_FREE_PAGES > > 2. don't add NR_FREE_PAGES when it is freed and the migratetype is > MIGRATE_ISOLATE > > 3. dec NR_FREE_PAGES when offlining isolated pages. > > 4. add NR_FREE_PAGES when undoing isolate pages. > > When we come to step 3, all pages are in MIGRATE_ISOLATE list, and > NR_FREE_PAGES are right. When we come to step4, all pages are not in > buddy system, so we don't change NR_FREE_PAGES in this step, but we change > NR_FREE_PAGES in step3. So NR_FREE_PAGES is wrong after offlining pages. > So there is no need to change NR_FREE_PAGES in step3. > > This patch also fixs a problem in step2: if the migratetype is > MIGRATE_ISOLATE, we should not add NR_FRR_PAGES when we remove pages from > pcppages. > > Signed-off-by: Wen Congyang <wency@cn.fujitsu.com> > Cc: David Rientjes <rientjes@google.com> > Cc: Jiang Liu <liuj97@gmail.com> > Cc: Len Brown <len.brown@intel.com> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Christoph Lameter <cl@linux.com> > Cc: Minchan Kim <minchan.kim@gmail.com> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> > Cc: Dave Hansen <dave@linux.vnet.ibm.com> > Cc: Mel Gorman <mel@csn.ul.ie> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > mm/page_alloc.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5b74de6..a7cd2d1 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -667,11 +667,13 @@ static void free_pcppages_bulk(struct zone *zone, int count, > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > __free_one_page(page, zone, 0, mt); > trace_mm_page_pcpu_drain(page, 0, mt); > - if (is_migrate_cma(mt)) > - __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1); > + if (likely(mt != MIGRATE_ISOLATE)) {
Hi Congyang, I think mt != MIGRATE_ISOLATE is always true here, page from PCP's migratetype < MIGRATE_PCPTYPES. When isolate page, we change pageblock's migratetype to MIGRATE_ISOLATE, but set_freepage_migratetype() isn't called. Maybe we can use mt = get_pageblock_migratetype() here ?
Thanks, Jianguo Wu.
> + __mod_zone_page_state(zone, NR_FREE_PAGES, 1); > + if (is_migrate_cma(mt)) > + __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1); > + } > } while (--to_free && --batch_free && !list_empty(list)); > } > - __mod_zone_page_state(zone, NR_FREE_PAGES, count); > spin_unlock(&zone->lock); > } > > @@ -5987,8 +5989,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > list_del(&page->lru); > rmv_page_order(page); > zone->free_area[order].nr_free--; > - __mod_zone_page_state(zone, NR_FREE_PAGES, > - - (1UL << order)); > for (i = 0; i < (1 << order); i++) > SetPageReserved((page+i)); > pfn += (1 << order); >
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