[linux-lvm] walltime of pvs vs pvdisplay with 256 PVs

Mike Snitzer snitzer at gmail.com
Thu Nov 16 02:54:54 UTC 2006

I have a testbed with 256 PVs.  Running 'pvdisplay -c' takes .672 sec.
 Running 'pvs' takes 43sec!  I've tried this on RHEL4U3
(lvm2-2.02.01-1.3.RHEL4) and RHEL4U4 (lvm2-2.02.06-6.0.RHEL4).  lvm2
from U4 is actually slower than U3 on this issue (1m vs 43s).

With RHEL4U3, pvs -vvvvv shows that a single device gets opened 264
times yet pvdisplay -c -vvvvv only opens a single device 8 times.
With RHEL4U4, there are 261 opens for pvs and 5 opens for pvdisplay
-c.  Clearly there is something flawed in the pvs algorithm.  I can
dig deeper but I wanted to put this info out there in case others
might have some insight.

please advise, thanks.

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