On Tue, 1 Jul 2008, Miles Nordin wrote: > > bf> What is the relationship between the size of the memory > bf> reservation and thrashing? > > The problem is that size-capping is the only control we have over > thrashing right now. Maybe there are better ways to predict thrashing > than through reservation size, and maybe it's possible to design swap
To be clear, "thrashing" as pertains to the paging device is due to the application making random access to virtual memory which is larger than the amount of physical memory on the machine. This is very similar to random access to disk (i.e. not very efficient) and in fact it does cause random access to disk. In a well-designed VM system (Solaris is probably second to none), sequential access to virtual memory causes reasonably sequential I/O requests to disk. Stale or dirty pages are expunged as needed in order to clear space for new requests. If multiple applications are fighting over the same VM, then there can still be thrashing even if their access is orderly. If using more virtual address space than there is physical address space always leads to problems, then it would not have much value. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
