Hi Bart, On Thu, Sep 06, 2012 at 06:34:35PM +0200, Bartlomiej Zolnierkiewicz wrote: > > Hi, > > On Thursday 06 September 2012 04:53:38 Minchan Kim wrote: > > Normally, MIGRATE_ISOLATE type is used for memory-hotplug. > > But it's irony type because the pages isolated would exist > > as free page in free_area->free_list[MIGRATE_ISOLATE] so people > > can think of it as allocatable pages but it is *never* allocatable. > > It ends up confusing NR_FREE_PAGES vmstat so it would be > > totally not accurate so some of place which depend on such vmstat > > could reach wrong decision by the context. > > > > There were already report about it.[1] > > [1] 702d1a6e, memory-hotplug: fix kswapd looping forever problem > > > > Then, there was other report which is other problem.[2] > > [2] http://www.spinics.net/lists/linux-mm/msg41251.html > > > > I believe it can make problems in future, too. > > So I hope removing such irony type by another design. > > > > I hope this patch solves it and let's revert [1] and doesn't need [2]. > > > > * Changelog v1 > > * Fix from Michal's many suggestion > > > > Cc: Michal Nazarewicz <mina86@xxxxxxxxxx> > > Cc: Mel Gorman <mel@xxxxxxxxx> > > Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> > > Cc: Wen Congyang <wency@xxxxxxxxxxxxxx> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > > --- > > It's very early version which show the concept so I still marked it with RFC. > > I just tested it with simple test and works. > > This patch is needed indepth review from memory-hotplug guys from fujitsu > > because I saw there are lots of patches recenlty they sent to about > > memory-hotplug change. Please take a look at this patch. > > [...] > > > @@ -948,8 +954,13 @@ static int move_freepages(struct zone *zone, > > } > > > > order = page_order(page); > > - list_move(&page->lru, > > - &zone->free_area[order].free_list[migratetype]); > > + if (migratetype != MIGRATE_ISOLATE) { > > + list_move(&page->lru, > > + &zone->free_area[order].free_list[migratetype]); > > + } else { > > + list_del(&page->lru); > > + isolate_free_page(page, order); > > + } > > page += 1 << order; > > pages_moved += 1 << order; > > } > > Shouldn't NR_FREE_PAGES counter be decreased somewhere above? > > [ I can see that it is not modified in __free_pages_ok() and > free_hot_cold_page() because page is still counted as non-free one but > here situation is different AFAICS. ] > > I tested the patch locally here with CONFIG_CMA=y and it causes some > major problems for CMA (multiple errors from dma_alloc_from_contiguous() > about memory ranges being busy and allocation failures). > > [ I'm sorry that I don't know more details yet but the issue should be > easily reproducible. ] At the moment, I don't have a time to look into that so I will revisit in near future. Thanks for the review and test! > > Best regards, > -- > Bartlomiej Zolnierkiewicz > Samsung Poland R&D Center > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>