Thanks Dave for your explanations. On Mon, Sep 20, 2010 at 10:05:35AM +1000, Dave Chinner wrote: > FWIW, if you can work out the magic necessary (perhaps systemtap) it > woul dbe really interesting to know whether it is the same buffer > that is causing the latency every time (i.e. get the bp->b_bn field > from the metadata buffer). With the block number, we can use xfs_db > to dig out what the buffer actually is.... I'm working on a dev box right now so I just added a trace_printk() to print out the bp->b_bn field when the xfs_buf_lock blocks for more than 300ms. Here are some numbers (I can easily get a lot more): _xfs_buf_find: xfs_buf_lock blocked for 1843ms on bp->b_bn: 812730376 _xfs_buf_find: xfs_buf_lock blocked for 1504ms on bp->b_bn: 406702514 _xfs_buf_find: xfs_buf_lock blocked for 307ms on bp->b_bn: 881190896 _xfs_buf_find: xfs_buf_lock blocked for 433ms on bp->b_bn: 406703400 _xfs_buf_find: xfs_buf_lock blocked for 420ms on bp->b_bn: 541595968 _xfs_buf_find: xfs_buf_lock blocked for 308ms on bp->b_bn: 44945968 _xfs_buf_find: xfs_buf_lock blocked for 702ms on bp->b_bn: 406027744 _xfs_buf_find: xfs_buf_lock blocked for 454ms on bp->b_bn: 474486504 _xfs_buf_find: xfs_buf_lock blocked for 869ms on bp->b_bn: 881195976 _xfs_buf_find: xfs_buf_lock blocked for 387ms on bp->b_bn: 1287891544 _xfs_buf_find: xfs_buf_lock blocked for 397ms on bp->b_bn: 1220116224 _xfs_buf_find: xfs_buf_lock blocked for 461ms on bp->b_bn: 2101644280 _xfs_buf_find: xfs_buf_lock blocked for 312ms on bp->b_bn: 338919728 _xfs_buf_find: xfs_buf_lock blocked for 356ms on bp->b_bn: 1016769536 _xfs_buf_find: xfs_buf_lock blocked for 593ms on bp->b_bn: 474488848 _xfs_buf_find: xfs_buf_lock blocked for 323ms on bp->b_bn: 1022248984 I should say that not every one of these results in a stall in my application, since my app needs to generate a page fault while that lock is held. What do I need to do to convert the block numbers to a buffer? Thanks, Shawn _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
