linux-kernel - Re: [PATCH 26/35] Use the per-cpu allocator for orders up to PAGE_ALLOC_COSTLY

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Message-ID: <alpine.DEB.1.10.0903161222070.32577@qirst.com>
Date:	Mon, 16 Mar 2009 12:26:07 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Linux Memory Management List <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 26/35] Use the per-cpu allocator for orders up to
 PAGE_ALLOC_COSTLY_ORDER

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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