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

From: Nick Piggin
Date: Tue Sep 11 2007 - 02:47:12 EST


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@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> 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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