On 10/08/2014, 03:26 PM, Johannes Weiner wrote:
> Hi Greg,
>
> the following should apply all the way back to 3.12. Thanks!
>
> ---
>
> From 1eedd7e702d68d9cb364ca32264dce26f675969b Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@xxxxxxxxxxx>
> Date: Thu, 2 Oct 2014 00:00:41 +0000
> Subject: [patch] mm: page_alloc: fix zone allocation fairness on UP
>
> commit abe5f972912d086c080be4bde67750630b6fb38b upstream.
>
> The zone allocation batches can easily underflow due to higher-order
> allocations or spills to remote nodes. On SMP that's fine, because
> underflows are expected from concurrency and dealt with by returning 0.
> But on UP, zone_page_state will just return a wrapped unsigned long, which
> will get past the <= 0 check and then consider the zone eligible until its
> watermarks are hit.
>
> 3a025760fc15 ("mm: page_alloc: spill to remote nodes before waking
> kswapd") already made the counter-resetting use atomic_long_read() to
> accomodate underflows from remote spills, but it didn't go all the way
> with it. Make it clear that these batches are expected to go negative
> regardless of concurrency, and use atomic_long_read() everywhere.
>
> Fixes: 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy")
> Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reported-by: Leon Romanovsky <leon@xxxxxxx>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Mel Gorman <mgorman@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> [3.12+]
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> mm/page_alloc.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a280f772bc66..eccad8b618fc 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1938,7 +1938,7 @@ zonelist_scan:
> if (alloc_flags & ALLOC_FAIR) {
> if (!zone_local(preferred_zone, zone))
> continue;
> - if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0)
> + if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0)
> continue;
> }
> /*
Hi, this does not apply to 3.12. It looks like this in there:
if (alloc_flags & ALLOC_FAIR) {
if (!zone_local(preferred_zone, zone))
break;
if (zone_is_fair_depleted(zone)) {
nr_fair_skipped++;
continue;
}
}
How should I resolve that conflict?
thanks,
--
js
suse labs
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