linux-kernel - Re: [PATCH 2/2] page-allocator: Maintain rolling count of pages to free from the PCP

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Message-ID: <84144f020908280516y6473a531n3f11f3e86251eba4@mail.gmail.com>
Date:	Fri, 28 Aug 2009 15:16:34 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] page-allocator: Maintain rolling count of pages to 
	free from the PCP

Hi Mel,

On Fri, Aug 28, 2009 at 11:44 AM, Mel Gorman<mel@....ul.ie> wrote:
> -               page = list_entry(list->prev, struct page, lru);
> -               /* have to delete it as __free_one_page list manipulates */
> -               list_del(&page->lru);
> -               trace_mm_page_pcpu_drain(page, 0, migratetype);
> -               __free_one_page(page, zone, 0, migratetype);
> +               do {
> +                       page = list_entry(list->prev, struct page, lru);
> +                       /* must delete as __free_one_page list manipulates */
> +                       list_del(&page->lru);
> +                       __free_one_page(page, zone, 0, migratetype);
> +                       trace_mm_page_pcpu_drain(page, 0, migratetype);

This calls trace_mm_page_pcpu_drain() *after* __free_one_page(). It's
probably not a good idea as __free_one_page() can alter the struct
page in various ways.

> +               } while (--count && --batch_free && !list_empty(list));
>        }
>        spin_unlock(&zone->lock);
>  }
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