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. -- Mel Gorman SUSE Labs -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>