Re: [PATCH 26/35] Use the per-cpu allocator for orders up toPAGE_ALLOC_COSTLY_ORDER

[Christoph Lameter]

On Mon, 16 Mar 2009, Mel Gorman wrote:

> -static void free_hot_cold_page(struct page *page, int cold)
> +static void free_hot_cold_page(struct page *page, int order, int cold)
>  {
>  	struct zone *zone = page_zone(page);
>  	struct per_cpu_pages *pcp;
>  	unsigned long flags;
>  	int clearMlocked = PageMlocked(page);
>
> +	/* SLUB can return lowish-order compound pages that need handling */
> +	if (order > 0 && unlikely(PageCompound(page)))
> +		if (unlikely(destroy_compound_page(page, order)))
> +			return;
> +

Isnt that also true for stacks and generic network objects ==- 8k?

>  again:
>  	cpu  = get_cpu();
> -	if (likely(order == 0)) {
> +	if (likely(order <= PAGE_ALLOC_COSTLY_ORDER)) {
>  		struct per_cpu_pages *pcp;
> +		int batch;
> +		int delta;
>
>  		pcp = &zone_pcp(zone, cpu)->pcp;
> +		batch = max(1, pcp->batch >> order);
>  		local_irq_save(flags);
>  		if (!pcp->count) {
> -			pcp->count = rmqueue_bulk(zone, 0,
> -					pcp->batch, &pcp->list, migratetype);
> +			delta = rmqueue_bulk(zone, order, batch,
> +					&pcp->list, migratetype);
> +			bulk_add_pcp_page(pcp, order, delta);
>  			if (unlikely(!pcp->count))
>  				goto failed;

The pcp adds a series of order N pages if an order N alloc occurs and the
queue is empty?

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