pt-diskstats: rd_avkb & wr_avkb derived incorrectly

[Aurimas Mikalauskas]

/proc/diskstats displays sectors read and sectors written in columns #6 and #10. Sectors are typically 512b units, however pt-diskstats assumes one sector = 1kb. Therefore, it would be best either to rename them to "rd_avsct" and "wr_avsct", or divide the number by 2 to display kilobytes.

Here's a sample that clearly shows that numbers do not add up. I've written 1MB with dd using oflag=direct bs=131072 count=8:

  #ts device rd_s rd_avkb rd_mb_s rd_mrg rd_cnc rd_rt wr_s wr_avkb wr_mb_s wr_mrg wr_cnc wr_rt busy in_prg
  {1} sdb 0.0 0.0 0.0 0% 0.0 0.0 7.9 256.0 1.0 0% 0.0 0.0 0% 0

Thank you,
Aurimas

[Baron Schwartz (baron-xaprb)]

Let's keep the column name as-is and fix the math.

[Daniel Nichter (daniel-nichter)]

For the record, Brian says that there are test cases which were fixed by the new code.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-427