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

[Michael Loftis]

>Number:         141305
>Category:       kern
>Synopsis:       FreeBSD ZFS+sendfile severe performance issues (no cache)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Dec 08 22:50:01 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Michael Loftis
>Release:        8.0
>Organization:
>Environment:
FreeBSD cs11.stilenet.com 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:02:08 UTC 2009     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
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.
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: