[LU-12578] obdfilter-survey w/echo-client does not gain from direct-io optimizations

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.13.0
• Assignee: Shaun Tancheff
• Reporter: Shaun Tancheff

Description

During testing on SSD platform this was reported:

CPU usage is in 95-100% range during obdfilter-survey. The perf trace looks very much like if LU-11347 is not applied but it is and OSS caches are disabled.

This is due to the lifetime of pages vs the obdfilter/obdecho lifetime:

dt_bufs_get / osd_bufs_get does allocates pages while
dt_bufs_put / osd_bufs_put marks the pages up-to-date and recycles them.
This is the typical pattern for longer lived osd threads.

For obdecho the threads are short lived and so the pattern matches
init/get/put/fini meaning the survey may not be a clear representation of actual osd performance.

 

Issue Links

• is related to: LU-12707 mds-survey test 1 crashes with a NULL pointer dereference in echo_object_free()