On Tue, Jun 28, 2011 at 9:52 PM, Mel Gorman <mgorman@xxxxxxx> wrote: > On Mon, Jun 27, 2011 at 03:53:04PM +0900, Minchan Kim wrote: >> On Fri, Jun 24, 2011 at 11:44 PM, Mel Gorman <mgorman@xxxxxxx> wrote: >> > When deciding if kswapd is sleeping prematurely, the classzone is >> > taken into account but this is different to what balance_pgdat() and >> > the allocator are doing. Specifically, the DMA zone will be checked >> > based on the classzone used when waking kswapd which could be for a >> > GFP_KERNEL or GFP_HIGHMEM request. The lowmem reserve limit kicks in, >> > the watermark is not met and kswapd thinks its sleeping prematurely >> > keeping kswapd awake in error. >> >> >> I thought it was intentional when you submitted a patch firstly. > > It was, it also wasn't right. > >> "Kswapd makes sure zones include enough free pages(ie, include reserve >> limit of above zones). >> But you seem to see DMA zone can't meet above requirement forever in >> some situation so that kswapd doesn't sleep. >> Right? >> > > Right. > >> > >> > Reported-and-tested-by: Pádraig Brady <P@xxxxxxxxxxxxxx> >> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> >> > --- >> > mm/vmscan.c | 2 +- >> > 1 files changed, 1 insertions(+), 1 deletions(-) >> > >> > diff --git a/mm/vmscan.c b/mm/vmscan.c >> > index 9cebed1..a76b6cc2 100644 >> > --- a/mm/vmscan.c >> > +++ b/mm/vmscan.c >> > @@ -2341,7 +2341,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, >> > } >> > >> > if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), >> > - classzone_idx, 0)) >> > + i, 0)) >> >> Isn't it better to use 0 instead of i? >> > > I considered it but went with i to compromise between making sure zones > included enough free pages without requiring that ZONE_DMA meet an > almost impossible requirement when under continual memory pressure. I see. Thanks, Mel. -- 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