linux-kernel - Re: [patch] mm/vmalloc: remove block allocation bitmap

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Message-ID: <20110420163954.GA7297@infradead.org>
Date:	Wed, 20 Apr 2011 12:39:54 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] mm/vmalloc: remove block allocation bitmap

On Wed, Apr 20, 2011 at 10:46:47AM +0100, Mel Gorman wrote:
> It'd be interesting but for the purposes of this patch I think it
> would be more useful to see the results of some benchmark that is vmap
> intensive. Something directory intensive running on XFS should do the
> job just to confirm no regression, right? A profile might indicate
> how often we end up scanning the full list, finding it dirty and
> calling new_vmap_block but even if something odd showed up there,
> it would be a new patch.

Note that the default mkfs.xfs options will not trigger any vmap
calls at runtime.  You'll need a filesystem with a large directory
block size to trigger heavy vmap usage.

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