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Date: Fri, 26 Mar 2010 20:34:31 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 00 of 41] Transparent Hugepage Support #15
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Marcelo Tosatti <mtosatti@redhat.com>, Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>, Izik Eidus <ieidus@redhat.com>, Hugh Dickins <hugh.dickins@tiscali.co.uk>, Nick Piggin <npiggin@suse.de>, Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>, Dave Hansen <dave@linux.vnet.ibm.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Chris Wright <chrisw@sous-sol.org>, bpicco@redhat.com, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Balbir Singh <balbir@linux.vnet.ibm.com>, Arnd Bergmann <arnd@arndb.de>, "Michael S. Tsirkin" <mst@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Johannes Weiner <hannes@cmpxchg.org>
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On Fri, Mar 26, 2010 at 01:44:23PM -0500, Christoph Lameter wrote:
> TLB pressure. Huge pages would accellerate SLUB since more objects can be
> served from the same page than before.

Agreed. I see it fallbacks to 4k instead of gradually going down, but
that was my point, doing the fallback and entry alloc_pages N without
internal buddy support would be fairly inefficient. This is why is
suggest this logic to be outside of slab/slub, in theory even slab
could be a bit faster thanks to large TLB on newly allocated slab
objects. I hope Mel's code already takes care of all of this.

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