This feature request can be broken down into 4 items: 1) Kernel changes for dm to use the existing kernel I/O stats mechanism; 2) A new kernel dm module to gather sophisticated customised stats; 3) Simple userspace tools changes to make it easy to use (2); 4) Sophisticated userspace tools (and gui) changes to get the best out of (2). I'm going to use this bugzilla to cover 1 and 2 ('kernel' component). Someone might like to raise new ones to cover 3 and 4 (device-mapper / lvm2 / lvm2 GUI components).
The patch for (1) is simple - needs a review, but certainly feasible for U3. The patch for (2) also exists but is more complex - not reviewed properly yet, API needs more work, but might be possible to include it in some form in U3 if there's time.
*** Bug 143390 has been marked as a duplicate of this bug. ***
*** Bug 170693 has been marked as a duplicate of this bug. ***
Created attachment 121243 [details] test cases for dm diskstat Test cases for dm diskstat. To complete this test, timing information collected by BZ#173398 is also needed. - Criteria for read_ticks, write_ticks, io_ticks may be too strict and sometimes cause false negative. Needs several trials to avoid it. - There may be better/finer criterion for time_in_queue.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2006-0132.html