From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 097596B0047 for ; Fri, 18 Dec 2009 14:17:55 -0500 (EST) Message-ID: <4B2BD55A.10404@sgi.com> Date: Fri, 18 Dec 2009 11:17:46 -0800 From: Mike Travis MIME-Version: 1.0 Subject: Re: [PATCH 00 of 28] Transparent Hugepage support #2 References: <4B2A8D83.30305@redhat.com> <20091218051210.GA417@elte.hu> <1261161677.27372.1629.camel@nimitz> In-Reply-To: <1261161677.27372.1629.camel@nimitz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Dave Hansen Cc: Christoph Lameter , Ingo Molnar , Rik van Riel , Andrea Arcangeli , linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Izik Eidus , Hugh Dickins , Nick Piggin , Mel Gorman , Andi Kleen , Benjamin Herrenschmidt , KAMEZAWA Hiroyuki , Chris Wright , Andrew Morton , "Stephen C. Tweedie" List-ID: Dave Hansen wrote: > On Fri, 2009-12-18 at 12:28 -0600, Christoph Lameter wrote: >> On Fri, 18 Dec 2009, Ingo Molnar wrote: >>> Note that it became more relevant in the past few years due to the arrival of >>> low-latency, lots-of-iops and cheap SSDs. Even on a low end server you can buy >>> a good 160 GB SSD for emergency swap with fantastic latency and for a lot less >>> money than 160 GB of real RAM. (which RAM wont even fit physically on typical >>> mainboards, is much more expensive and uses up more power and is less >>> servicable) >> Swap occurs in page size chunks. SSDs may help but its still a desaster >> area. You can only realistically use swap in a batch environment. It kills >> desktop performance etc etc. > > True... Let's say it takes you down to 20% of native performance. > There are plenty of cases where people are selling Xen or KVM slices > where 20% of native performance is more than *fine*. It may also let > you have VMs that are 3x more dense than they would be able to be > otherwise. Yes, it kills performance, but performance isn't everything. > > For many people price/performance is much more important, and swapping > really helps the price side of that equation. > > We *do* need to work on making swap more useful in a wide range of > workloads, especially since SSDs have changed some of our assumptions > about swap. I just got a laptop SSD this week, and tuned swappiness so > that I'd get some more swap activity. Things really bogged down, so I > *know* there's work to do there. > > -- Dave Interesting discussion about SSD's. I was under the impression that with the finite number of write cycles to an SSD, that unnecessary writes were to be avoided? Mike -- 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: email@kvack.org