8.0-R-p2 ZFS: unixbench causing kmem exhaustion panic

Doug Poland doug at polands.org
Wed Jan 13 17:31:47 UTC 2010


I'm trying to get an 8.0-RELEASE-p2 amd64 box to not crash when
running benchmarks/unixbench.  The box in question has 4GB RAM running
6 SCSI disks in a RAID1Z.

dmesg | grep memory
real memory  = 4294967296 (4096 MB)
avail memory = 3961372672 (3777 MB)

zpool status
  pool: bethesda
 state: ONLINE
 scrub: none requested

        NAME           STATE     READ WRITE CKSUM
        bethesda       ONLINE       0     0     0
          raidz1       ONLINE       0     0     0
            gpt/disk0  ONLINE       0     0     0
            gpt/disk1  ONLINE       0     0     0
            gpt/disk2  ONLINE       0     0     0
            gpt/disk3  ONLINE       0     0     0
            gpt/disk4  ONLINE       0     0     0
            gpt/disk5  ONLINE       0     0     0

It appears unixbench causes the mem exhaustion when running the fstime
/ fsbuffer / fsdisk programs, depending on what I've got in

I began with a system with no tunables in /boot/loader.conf
(vm.kmem_size and vm.kmem_size_max).  Then I tried increasing
vm.kmem_size and vm.kmem_size_max a GB at a time, until I was at 4GB.

At every increase, the system panicked with a kmem exhaustion, until I
used the 4GB settings.  At that time, the system system became
unresponsive and had to be reset.

So the question is, can ZFS be tuned to not panic or hang no matter
what I throw at it?  In this case, it's the ancient and innocuous
unixbench utility.

This is a test box right now and I'm more than willing to try various
tests or tweaks to get 8.x FreeBSD/ZFS into a stable state.


More information about the freebsd-questions mailing list