On Thu, Jun 24, 2010 at 11:30:44PM +0300, Yannis Klonatos wrote: > Hello all, > > Along with my other (yet pending :-( ) question/issue, I > have another question (i hope this is the last :-) ) > now. > I would like to measure the hit ratio of the metadata > accesses of XFS (inode+internal buffers). It is my > understanding that XFS uses its own data structures, and does not > rely on the buffercache mechanisms of > the Linux kernel. However, even doing so, there may be cases that > the metadata may not fit in the RAM, > and I/O operations are required to fetch them from the underlying > storage. I have found out that there are > two places that XFS uses the submit_bio function. If i add some > counters there, would it suffice to measure all > the metadata misses? > Or is this information available in one (or more) of the > xfs_stats counters? And if so, what do i need to sum > up in order to get the total metadata hit and miss ratio? Start by looking here: http://xfs.org/index.php/Runtime_Stats But you probably want some of the buf counters which are undocumented on that page, so a rough description of them is (from PCP): $ pminfo -t xfs.buffer xfs.buffer.get [number of request buffer calls] xfs.buffer.create [number of buffers created] xfs.buffer.get_locked [number of requests for a locked buffer which succeeded] xfs.buffer.get_locked_waited [number of requests for a locked buffer which waited] xfs.buffer.busy_locked [number of non-blocking requests for a locked buffer which failed] xfs.buffer.miss_locked [number of requests for a locked buffer which failed due to no buffer] xfs.buffer.page_retries [number of retry attempts when allocating a page for insertion in a buffer] xfs.buffer.page_found [number of hits in the page cache when looking for a page] xfs.buffer.get_read [number of buffer get calls requiring immediate device reads] So you might be able to get something from those stats. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
