I've just been reading about the mergemem kernel patch. I haven't noticed any reference to it on this list before, so thought I'd draw it to your attention and ask if anyone has any experience with it. For details see: http://www.mondoshawan.ml.org/mergemem/ http://www.complang.tuwien.ac.at/ulrich/mergemem/ In brief, mergemem examines the memory belonging to processes running the same program and marks identical pages as 'read-only and 'copy-on-write'. This is in addition to the normal steps that the Linux kernel takes to share memory. The JVM initialises large amounts of data memory when it loads its class files. Most of this memory will never be written to during the life of the JVM, and separate instances of the JVM will load the same stuff. There thus seems to be considerable scope for sharing memory. At the mergemem site they quote memory usage figures for JDK 1.1.3 running some of the demo applets: First instance of JVM 12488 kB Further instance w/o mergemem 7612 kB Further intstance with mergemem 2452 kB This looks like a very promising approach for those who need to run multiple instances of the JVM. Ron Yorston direct phone: +44 1628 587074 PGS Tigress, phone: +44 1628 587000 Grenfell House, Grenfell Road, fax: +44 1628 587111 Maidenhead, Berks, e-mail: [EMAIL PROTECTED] SL6 1ES, UK
