site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com S+E -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Technical Support * Networking, Communications, Hardware _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... At 10:00 -0800 7/1/05, Richard Jackson wrote: I'm using the "fs_usage" utility to help me optimize my application's I/O calls, and I see a lot of events labeled "CACHE_HIT". Could someone explain what these are? (VM paging? File System caching?) This corresponds to the symbol DBG_CACHE_HIT_FAULT. It indicates that the process took a page fault but the page was found in the cache. [Mac OS X has a Unified Buffer Cache (between the file system and VM), so there's no distinction between VM and file system cache.] This is in contrast to "PAGE_IN" (DBG_PAGEIN_FAULT) which indicates that the system took a page fault that required a read from disk. To understand the exact logic, take a look at the vm_fault routine in "xnu/osfmk/vm/vm_fault.c". This email sent to site_archiver@lists.apple.com