Can someone explain this result?

devsk devsku at gmail.com
Sun May 8 01:46:40 EDT 2011


# time find rsynced/|wc -l
384736

real    0m50.615s
user    0m0.350s
sys     0m19.404s

# time find rsynced/|wc -l
384736

real    2m5.708s
user    0m0.315s
sys     0m5.185s

# time find rsynced/|wc -l
384736

real    1m53.062s
user    0m0.350s
sys     0m4.418s

The FS is idle at this time and so is the pool. This is not rootfs.
Its a RAIDZ1 pool with dedup and compression on. There is an SSD
configured as a cache device.

How is it possible that when I run the first time, I get the fastest
time while subsequent runs are slower by more than half. I am baffled.
And this is not the first time ZFS on Linux has done this: this has
been seen multiple times now because it did this when I was running
ZFS rootfs on my laptop.

-devsk



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