Re: [RFC PATCH 1/5] mm, page_alloc: support multiple pages allocation

[Dave Hansen <dave.hansen@intel.com>]

On 07/03/2013 01:34 AM, Joonsoo Kim wrote:
> -		if (page)
> +		do {
> +			page = buffered_rmqueue(preferred_zone, zone, order,
> +							gfp_mask, migratetype);
> +			if (!page)
> +				break;
> +
> +			if (!nr_pages) {
> +				count++;
> +				break;
> +			}
> +
> +			pages[count++] = page;
> +			if (count >= *nr_pages)
> +				break;
> +
> +			mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
> +			if (!zone_watermark_ok(zone, order, mark,
> +					classzone_idx, alloc_flags))
> +				break;
> +		} while (1);

I'm really surprised this works as well as it does.  Calling
buffered_rmqueue() a bunch of times enables/disables interrupts a bunch
of times, and mucks with the percpu pages lists a whole bunch.
buffered_rmqueue() is really meant for _single_ pages, not to be called
a bunch of times in a row.

Why not just do a single rmqueue_bulk() call?

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