On Nov 7, 2007 6:09 PM, Brian Nielsen <[EMAIL PROTECTED]> wrote: > I'm working on fine tuning my balance between MDC hits, VM paging rate, > Linux swap rate, and Linux guest use of memory for cache. The one piece > of data I'm missing is the hit ratio of the Linux cache. My research so > far has not turned up anything that reports this value. Anybody know if > this statistic is even available (SLES 9 & 10) and, if so, where to find > it?
There's no such metric right now. Future kernel levels have added a tracing facility in the block device layer, and proper processing of that can compute cache hit ratio (among others) from that trace. I'm in the process of building that gear. Actually, believe it or not - I just booted the system with the things in place for the first time. Analysis of a small portion of trace shows things like this: CPU0 (94,1): Reads Queued: 424, 11,332KiB Writes Queued: 146, 620KiB Read Dispatches: 402, 11,372KiB Write Dispatches: 87, 620KiB Reads Requeued: 0 Writes Requeued: 0 Reads Completed: 402, 11,372KiB Writes Completed: 87, 620KiB Read Merges: 24, 284KiB Write Merges: 59, 236KiB Read depth: 6 Write depth: 6 IO unplugs: 382 Timer unplugs: 20 Need some more digging to understand the numbers and see what I can get out of that. Rob -- Rob van der Heij Velocity Software, Inc http://velocitysoftware.com/
