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Date: Mon, 5 Apr 2010 17:01:33 -0400
From: Chris Mason <chris.mason@oracle.com>
Subject: Re: [PATCH 00 of 41] Transparent Hugepage Support #17
Message-ID: <20100405210133.GE21620@think>
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, linux-mm@kvack.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>, Mike Travis <travis@sgi.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Christoph Lameter <cl@linux-foundation.org>, 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>, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
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On Mon, Apr 05, 2010 at 01:32:21PM -0700, Linus Torvalds wrote:
> 
> 
> On Mon, 5 Apr 2010, Pekka Enberg wrote:
> > 
> > AFAIK, most modern GCs split memory in young and old generation
> > "zones" and _copy_ surviving objects from the former to the latter if
> > their lifetime exceeds some threshold. The JVM keeps scanning the
> > smaller young generation very aggressively which causes TLB pressure
> > and scans the larger old generation less often.
> 
> .. my only input to this is: numbers talk, bullsh*t walks. 
> 
> I'm not interested in micro-benchmarks, either. I can show infinite TLB 
> walk improvement in a microbenchmark.

Ok, I'll bite.  I should be able to get some database workloads with
hugepages, transparent hugepages, and without any hugepages at all.

-chris

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