kern/141305: FreeBSD ZFS+sendfile severe performance issues (no cache)

Michael Loftis mloftis at
Tue Dec 8 22:50:02 UTC 2009

>Number:         141305
>Category:       kern
>Synopsis:       FreeBSD ZFS+sendfile severe performance issues (no cache)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Dec 08 22:50:01 UTC 2009
>Originator:     Michael Loftis
>Release:        8.0
FreeBSD 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:02:08 UTC 2009     root at  amd64
sendfile from ZFS filesystems does not appear to use the read cache, and may not be read combining either.  Serving files streaming media using default lighttpd setup on FreeBSD+ZFS we get 50+mbyte/sec disk I/O and *barely* 300-400mbit output.  Same hardware, same streaming media load, it saturates a gig-e connection with ~2mbyte/sec disk I/O.  This should be easy to reproduce with any HTTP benchmark suite and anything serving with sendfile on ZFS as lighttpd does.



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