Hi KOSAKi, On Tue, Jul 12, 2011 at 6:40 PM, KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > (2011/07/12 18:27), Minchan Kim wrote: >> Hi Mel, >> >> On Mon, Jul 11, 2011 at 10:01 PM, Mel Gorman <mgorman@xxxxxxx> wrote: >>> Zone reclaim is similar to direct reclaim in a number of respects. >>> PF_SWAPWRITE is used by kswapd to avoid a write-congestion check >>> but it's set also set for zone_reclaim which is inappropriate. >>> Setting it potentially allows zone_reclaim users to cause large IO >>> stalls which is worse than remote memory accesses. >> >> As I read zone_reclaim_mode in vm.txt, I think it's intentional. >> It has meaning of throttle the process which are writing large amounts >> of data. The point is to prevent use of remote node's free memory. >> >> And we has still the comment. If you're right, you should remove comment. >> " * and we also need to be able to write out pages for RECLAIM_WRITE >> * and RECLAIM_SWAP." >> >> >> And at least, we should Cc Christoph and KOSAKI. > > Of course, I'll take full ack this. Do you remember I posted the same patch > about one year ago. At that time, Mel disagreed me and I'm glad to see he changed > the mind. :) I remember that but I don't know why Mel didn't ack at that time. http://lkml.org/lkml/2010/8/5/44 Anyway, Hannes's bd2f6199cf is to introduce lumpy reclaim of zone_reclaim so it's natural to increase latency for getting big order pages(ie, it's a trade-off). And as I read about zone_reclaim_mode in Documentation/sysctl/vm.txt, I think big latency(ie, throttling of the process) is intentional to prevent stealing pages for other nodes. If I am not against this patch, at least, we need agreement of Christoph and others and if we agree this change, we changes vm.txt, too. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href