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POHMELFS vs NFS: dbench and the power of the local metadata cache


POHMELFS vs NFS dbench performance

Client and server machines have 8Gb of RAM and I ran single-threaded test to show the power of the local metadata cache, so get this data with a fair grain of salt.

POHMELFS served close to 160k operations over the network, while async in-kernel NFS ended up with this dump:

   1    643930    23.31 MB/sec  execute 149 sec   
   1    649695    23.37 MB/sec  cleanup 150 sec   
/bin/rm: cannot remove directory `/mnt//clients/client0/~dmtmp/ACCESS': Directory not empty
/bin/rm: cannot remove directory `/mnt//clients/client0/~dmtmp/SEED': Directory not empty
   1    649695    23.36 MB/sec  cleanup 150 sec   

More precise performance values:

POHMELFS   652.481 MB/sec
NFS         23.366 MB/sec

I’ve pushed POHMELFS update to the GIT, which includes a long-waiting switch from the own path cache to the system’s dcache (kudos to the one who exported dcache_lock to the modules :)

It will be likely pushed into the drivers/staging in a day or so.

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