From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Vrable Subject: Re: Copy-on-write memory to allow many more xenU domains per machine Date: Tue, 26 Oct 2004 15:19:55 -0700 Sender: xen-devel-admin@lists.sourceforge.net Message-ID: <20041026151955.B25506@cs.ucsd.edu> References: <20041026113042.C27518@cs.ucsd.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: ; from Ian.Pratt@cl.cam.ac.uk on Tue, Oct 26, 2004 at 08:43:30PM +0100 Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org On Tue, Oct 26, 2004 at 08:43:30PM +0100, Ian Pratt wrote: > > "Memory Resource Management in VMware ESX Server" by Carl Waldspurger > > has some numbers on memory sharing between VMs: > > http://www.usenix.org/events/osdi02/tech/waldspurger/waldspurger.pdf > > (This paper is also cited in the Xen SOSP 2003 paper.) > > > > Sharing between identical machines is good, though sharing between > > dissimilar machines is not as high as I remembered (copy-on-write > > sharing is able to save around 7-30% of memory in real-world testing). > > As I recall, Carl's results were on Windows, which might explain > why I was seeing rather less. Linux resident set sizes tend to be > smaller, and there's generally rather more diversity in the > install base (at least around here). Both were tested in that paper; Windows was at the high end of the scale and Linux at the low end: Reproducing Figure 5 from the paper in slightly abbreviated form: Guests % Shared % Reclaimed 10 x WinNT 42.9 32.9 9 x Linux 29.2 18.7 5 x Linux 10.0 7.2 "% Shared" is the fraction of pages which are shared; "% Reclaimed" measures how much memory sharing the pages is able to save. Three systems is still a limited test set. --Michael Vrable ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click