Can someone explain this result?

Christ Schlacta aarcane at aarcane.org
Sun May 8 03:24:33 EDT 2011


Only this g I can think of is a crappy cache device.  

devsk <devsku at gmail.com> wrote:

># 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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