From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: A scrub daemon (prezeroing) From: Nick Piggin In-Reply-To: References: <1106828124.19262.45.camel@hades.cambridge.redhat.com> <20050202153256.GA19615@logos.cnet> <20050202163110.GB23132@logos.cnet> <16898.46622.108835.631425@cargo.ozlabs.ibm.com> <16899.2175.599702.827882@cargo.ozlabs.ibm.com> Content-Type: text/plain Date: Fri, 04 Feb 2005 17:43:23 +1100 Message-Id: <1107499403.5461.32.camel@npiggin-nld.site> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Paul Mackerras , Rik van Riel , Marcelo Tosatti , David Woodhouse , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@osdl.org List-ID: On Thu, 2005-02-03 at 22:26 -0800, Christoph Lameter wrote: > On Fri, 4 Feb 2005, Paul Mackerras wrote: > > > As has my scepticism about pre-zeroing actually providing any benefit > > on ppc64. Nevertheless, the only definitive answer is to actually > > measure the performance both ways. > > Of course. The optimization depends on the type of load. If you use a > benchmark that writes to all pages in a page then you will see no benefit > at all. For a kernel compile you will see a slight benefit. For processing > of a sparse matrix (page tables are one example) a significant benefit can > be obtained. If you have got to the stage of doing "real world" tests, I'd be interested to see results of tests that best highlight the improvements. I imagine many general purpose server things wouldn't be helped much, because they'll typically have little free memory, and will be continually working and turning things over. A kernel compile on a newly booted system? Well that is a valid test. It is great that performance doesn't *decrease* in that case :P Of course HPC things may be a different story. It would be good to see your gross improvement on typical types of workloads that can best leverage this - and not just initial ramp up phases while memory is being faulted in, but the the full run time. Thanks, Nick -- 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: aart@kvack.org