Hi Johannes,
On Wed, Oct 08, 2014 at 09:26:04AM -0400, Johannes Weiner wrote:
> Hi Greg,
>
> the following should apply all the way back to 3.12. Thanks!
>
I see your backport has never made its way into the 3.16 kernel. Does
it still make sense to apply it, or was there a reason for not
applying it?
Cheers,
--
Luís
> ---
>
> 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;
> }
> /*
> @@ -5607,9 +5607,8 @@ static void __setup_per_zone_wmarks(void)
> zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1);
>
> __mod_zone_page_state(zone, NR_ALLOC_BATCH,
> - high_wmark_pages(zone) -
> - low_wmark_pages(zone) -
> - zone_page_state(zone, NR_ALLOC_BATCH));
> + high_wmark_pages(zone) - low_wmark_pages(zone) -
> + atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
>
> setup_zone_migrate_reserve(zone);
> spin_unlock_irqrestore(&zone->lock, flags);
> --
> 2.1.2
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html