linux-kernel - Re: [PATCH 7/13] Drain per-cpu lists when high-order allocations fail

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Date:	Tue, 11 Sep 2007 01:05:25 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Mel Gorman <mel@....ul.ie>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 7/13] Drain per-cpu lists when high-order allocations fail

On Monday 10 September 2007 21:22, Mel Gorman wrote:
> Per-cpu pages can accidentally cause fragmentation because they are free,
> but pinned pages in an otherwise contiguous block.  When this patch is
> applied, the per-cpu caches are drained after the direct-reclaim is entered
> if the requested order is greater than 0.  It simply reuses the code used
> by suspend and hotplug.

Does this help? I have a more general version which could go in
instead (independently of the anti fragmentation patches).

> Signed-off-by: Mel Gorman <mel@....ul.ie>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
>
>  mm/page_alloc.c |   24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
> linux-2.6.23-rc5-006-group-short-lived-and-reclaimable-kernel-allocations/m
>m/page_alloc.c
> linux-2.6.23-rc5-007-drain-per-cpu-lists-when-high-order-allocations-fail/m
>m/page_alloc.c ---
> linux-2.6.23-rc5-006-group-short-lived-and-reclaimable-kernel-allocations/m
>m/page_alloc.c	2007-09-02 16:20:31.000000000 +0100 +++
> linux-2.6.23-rc5-007-drain-per-cpu-lists-when-high-order-allocations-fail/m
>m/page_alloc.c	2007-09-02 16:20:48.000000000 +0100 @@ -852,6 +852,7 @@ void
> mark_free_pages(struct zone *zone)
>  	}
>  	spin_unlock_irqrestore(&zone->lock, flags);
>  }
> +#endif /* CONFIG_PM */
>
>  /*
>   * Spill all of this CPU's per-cpu pages back into the buddy allocator.
> @@ -864,7 +865,25 @@ void drain_local_pages(void)
>  	__drain_pages(smp_processor_id());
>  	local_irq_restore(flags);
>  }
> -#endif /* CONFIG_HIBERNATION */
> +
> +void smp_drain_local_pages(void *arg)
> +{
> +	drain_local_pages();
> +}
> +
> +/*
> + * Spill all the per-cpu pages from all CPUs back into the buddy allocator
> + */
> +void drain_all_local_pages(void)
> +{
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	__drain_pages(smp_processor_id());
> +	local_irq_restore(flags);
> +
> +	smp_call_function(smp_drain_local_pages, NULL, 0, 1);
> +}
>
>  /*
>   * Free a 0-order page
> @@ -1452,6 +1471,9 @@ nofail_alloc:
>
>  	cond_resched();
>
> +	if (order != 0)
> +		drain_all_local_pages();
> +
>  	if (likely(did_some_progress)) {
>  		page = get_page_from_freelist(gfp_mask, order,
>  						zonelist, alloc_flags);
>
> --
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> see: http://www.linux-mm.org/ .
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