Re: [patch 1/2] mm: page_alloc: reset aging cycle with GFP_THISNODE

[Rik van Riel <riel@redhat.com>]

On 02/25/2014 03:27 PM, Johannes Weiner wrote:
> Jan Stancek reports manual page migration encountering allocation
> failures after some pages when there is still plenty of memory free,
> and bisected the problem down to 81c0a2bb515f ("mm: page_alloc: fair
> zone allocator policy").
> 
> The problem is that page migration uses GFP_THISNODE and this makes
> the page allocator bail out before entering the slowpath entirely,
> without resetting the zone round-robin batches.  A string of such
> allocations will fail long before the node's free memory is exhausted.
> 
> GFP_THISNODE is a special flag for callsites that implement their own
> clever node fallback and so no direct reclaim should be invoked.  But
> if the allocations fail, the fair allocation batches should still be
> reset, and if the node is full, it should be aged in the background.
> 
> Make GFP_THISNODE wake up kswapd and reset the zone batches, but bail
> out before entering direct reclaim to not stall the allocating task.
> 
> Reported-by: Jan Stancek <jstancek@redhat.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Cc: <stable@kernel.org> # 3.12+

Acked-by: Rik van Riel <riel@redhat.com>

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