From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19])
	by kanga.kvack.org (Postfix) with SMTP id 246FE6B01F8
	for <linux-mm@kvack.org>; Tue,  6 Apr 2010 14:05:25 -0400 (EDT)
Message-ID: <4BBB77BC.60409@redhat.com>
Date: Tue, 06 Apr 2010 21:04:44 +0300
From: Avi Kivity <avi@redhat.com>
MIME-Version: 1.0
Subject: Re: [PATCH 00 of 41] Transparent Hugepage Support #17
References: <20100405232115.GM5825@random.random> <alpine.LFD.2.00.1004051636060.21411@i5.linux-foundation.org> <20100406011345.GT5825@random.random> <alpine.LFD.2.00.1004051836000.5870@i5.linux-foundation.org> <alpine.LFD.2.00.1004051917310.3487@i5.linux-foundation.org> <4BBB052D.8040307@redhat.com> <4BBB2134.9090301@redhat.com> <20100406131024.GA5288@laptop> <4BBB359D.1020603@redhat.com> <20100406134539.GC5288@laptop> <20100406165031.GA5825@random.random> <4BBB6FEC.9050205@redhat.com> <alpine.DEB.2.00.1004061259120.19151@router.home>
In-Reply-To: <alpine.DEB.2.00.1004061259120.19151@router.home>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-linux-mm@kvack.org
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>, Nick Piggin <npiggin@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Pekka Enberg <penberg@cs.helsinki.fi>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, Marcelo Tosatti <mtosatti@redhat.com>, Adam Litke <agl@us.ibm.com>, Izik Eidus <ieidus@redhat.com>, Hugh Dickins <hugh.dickins@tiscali.co.uk>, 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>, 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>
List-ID: <linux-mm.kvack.org>

On 04/06/2010 09:00 PM, Christoph Lameter wrote:
>
>> I don't think gcc is worst case.  Workloads that benefit from large pages are
>> those with bloated working sets that do a lot of pointer chasing and do little
>> computation in between.  gcc fits two out of three (just a partial score on
>> the first).
>>      
> Once you have huge pages you will likely start to optimize for locality.
>
> Pointer chasing is bad even with huge pages if you go between multiple
> huge pages and you are beyond the number of huge tlb entries supported by
> the cpu.
>    

A hugetlb miss is serviced from the L2 or L3 cache.  A smalltlb miss is 
serviced from main memory.  The miss rate is important, but not nearly 
as important as fill latency.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>