lkml.org 
[lkml]   [2011]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH 3/4] mm: vmscan: Evaluate the watermarks against the correct classzone
    From
    On Tue, Jun 28, 2011 at 9:52 PM, Mel Gorman <mgorman@suse.de> 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@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.

    I see.
    Thanks, Mel.

    --
    Kind regards,
    Minchan Kim
    --
    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/

    \
     
     \ /
      Last update: 2011-06-29 01:25    [W:0.043 / U:0.376 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site