linux-kernel - Re: [patch 3/3] slub: sort parital list when thrashing

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Message-ID: <alpine.DEB.1.10.0903301040160.13333@qirst.com>
Date:	Mon, 30 Mar 2009 10:41:03 -0400 (EDT)
From:	Christoph Lameter <cl@...ux.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Martin Bligh <mbligh@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/3] slub: sort parital list when thrashing

On Sun, 29 Mar 2009, David Rientjes wrote:

> @@ -1720,6 +1727,15 @@ checks_ok:
>  	if (unlikely(!prior)) {
>  		add_partial(get_node(s, page_to_nid(page)), page, 1);
>  		stat(c, FREE_ADD_PARTIAL);
> +	} else if (c->slowpath_allocs >= SLAB_THRASHING_THRESHOLD) {
> +		/*
> +		 * If the cache is actively slab thrashing, it's necessary to
> +		 * move partial slabs to the head of the list so there isn't
> +		 * excessive partial list scanning while holding list_lock.
> +		 */
> +		if (!skip_partial(s, page))
> +			move_partial_to_head(get_node(s, page_to_nid(page)),
> +					     page);
>  	}
>
>  out_unlock:
>

This again adds code to a pretty hot path.

What is the impact of the additional hot path code?

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