FreeBSD 8.2 Release, ZFS + Samba, running out of memory

[Henner Heck]

Here are my testresults:

*Disabling sendfile in smb.conf *(no patching yet)
- free memory drops to 570M and stays there
- copy speed from share 75MB/s, CPU load 50%
    (why not 100% and higher speed?)

*Patched kernel with patch 218795*
- without sendfile  
    Copying works.
- with sendfile  
   Copy speed often drops to zero after several hundred megabytes,
     no more data is transmitted, the BSD machine is 100% idle and
responsive.
     After some time Total Commander claims that the file cannot be copied,
     on retry it sometimes copies the file, but the problem will usually
come up
     with the same file again or one of the next files.

The speed in both cases is between 40-70MB/s, CPU load is 30-50%,
    the free memory drops to about 250M, no running out of memory.

*Other observations*
A process named "intr" causes about 20% CPU load when copying.
I wonder why.

*Conclusions*
When using sendfile the patch replaced a freezing system with unreliable
copying. Without sendfile there seems to be no problem.

I am a bit dissapointed with the speed, since the CPU is not at all
maxed out.
The NIC is a PCIe Intel CT 1000 (I hadn't mentioned that before.)
Any idea where the bottleneck might be?

Regards,
Henner Heck