From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kip Macy Subject: Re: copy on write memory Date: Thu, 18 Nov 2004 11:16:34 -0800 (PST) Message-ID: <20041118111500.L39146@demos.bsdclusters.com> References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Keir Fraser Cc: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org It doesn't sound like the performance benefit would justify the added management complexity for xen. -Kip On Thu, 18 Nov 2004, Keir Fraser wrote: > > > > > > Is there any documentation on the semantics of DCSS and the hypervisor > > > services that are used? It would be interesting to see if Xen ought to > > > have some similar concept. > > > > This doesn't really answer your question - but the closest your likely > > to get is at their pubs: > > > > http://www.vm.ibm.com/pubs/ > > There's a manual called "How to Improve the Performance of Linux on > z/VM with Execute-In-Place Technology", which is easily googled for. > Turns out that DCSSs are pretty simple things -- just a blob of > physmem that is mapped into phys address space of every Linux > instance, and contains a read-only filesystem image. xip2fs is a > simple read-only fs that serves mmap() requests directly out of the > shared DCSS rather than the private block cache. Looks tedious to > manage because the whole filesystem takes up space in every Linux > memory map all the time, no matter whether a particular file/block is > being used. So you have to be careful to put only frequently accessed > and highly shared files in the filesystem and use twisted symlinks to > link in from their usual location into the mounted xip2fs filesystem. > > -- Keir > > > ------------------------------------------------------- > This SF.Net email is sponsored by: InterSystems CACHE > FREE OODBMS DOWNLOAD - A multidimensional database that combines > robust object and relational technologies, making it a perfect match > for Java, C++,COM, XML, ODBC and JDBC. www.intersystems.com/match8 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xen-devel > ------------------------------------------------------- This SF.Net email is sponsored by: InterSystems CACHE FREE OODBMS DOWNLOAD - A multidimensional database that combines robust object and relational technologies, making it a perfect match for Java, C++,COM, XML, ODBC and JDBC. www.intersystems.com/match8