I have made a number of what I would call non-structural changes to ZFS (no changes to file system semantics or space allocation) to improve the performance of ZFS, as imported in to FreeBSD, in my client's environment. Pawel Dawidek has asked that I try to get my changes pushed upstream to minimize the pain involved in importing future ZFS versions.
Among other things I found that there was a great deal of lock contention in prefetch. In light of the fact that prefetch is a purely opportunistic operation, it does not make sense to me to delay productive work in order to issue a prefetch request. In the following patch I have changed the locking operations to be 'trylock's, failing the operation if the lock acquisition does not succeed. http://people.freebsd.org/~kmacy/dmu_zfetch_trylock.patch Constructive criticism, feedback, etc. is welcome. Thanks, Kip -- When harsh accusations depart too far from the truth, they leave bitter consequences. --Tacitus
