Messages in this thread | | | Date | Tue, 28 Jun 2011 13:52:49 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 3/4] mm: vmscan: Evaluate the watermarks against the correct classzone |
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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@suse.de> 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@draigBrady.com> > > Signed-off-by: Mel Gorman <mgorman@suse.de> > > --- > > 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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