linux-kernel - Re: No, really, stop trying to delete slab until you've finished making slub perform as well

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Message-ID: <48A3DBAC.6010109@cs.helsinki.fi>
Date:	Thu, 14 Aug 2008 10:15:56 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KOSAKI Motohiro <m-kosaki@...es.dti.ne.jp>,
	Matthew Wilcox <matthew@....cx>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Mel Gorman <mel@...net.ie>, andi@...stfloor.org,
	Rik van Riel <riel@...hat.com>
Subject: Re: No, really, stop trying to delete slab until you've finished
 making slub perform as well

Hi Christoph,

Christoph Lameter wrote:
> The obvious fix is to avoid allocating another slab on conflict but how will
> this impact performance?
> 
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2008-08-13 08:06:00.000000000 -0500
> +++ linux-2.6/mm/slub.c	2008-08-13 08:07:59.000000000 -0500
> @@ -1253,13 +1253,11 @@
>  static inline int lock_and_freeze_slab(struct kmem_cache_node *n,
>  							struct page *page)
>  {
> -	if (slab_trylock(page)) {
> -		list_del(&page->lru);
> -		n->nr_partial--;
> -		__SetPageSlubFrozen(page);
> -		return 1;
> -	}
> -	return 0;
> +	slab_lock(page);
> +	list_del(&page->lru);
> +	n->nr_partial--;
> +	__SetPageSlubFrozen(page);
> +	return 1;
>  }

This patch hard locks  on my 2-way 64-bit x86 machine (sysrq doesn't 
respond) when I run hackbench.

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