ZFS performance help sought

[Mason Loring Bliss]

On Thu, Jan 21, 2016 at 06:28:10PM -0500, Mason Loring Bliss wrote:

> All that said, I wasn't setting write_limit_override, so I'm trying that, and
> I'm cutting the txg.timeout back a couple seconds more.

Well, that didn't help. System's still really choppy.

last pid:  1707;  load averages:  9.20,  4.75,  2.14    up 0+00:09:35  18:53:03
55 processes:  1 running, 54 sleeping
CPU:  2.1% user,  0.0% nice, 62.6% system,  0.5% interrupt, 34.8% idle
Mem: 323M Active, 331M Inact, 4589M Wired, 8928K Cache, 2677M Free
ARC: 4096M Total, 916M MFU, 2303M MRU, 845M Anon, 17M Header, 15M Other
Swap: 8192M Total, 8192M Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU COMMAND
 1501 root          1  33    0 42248K  3616K dmu_tx  1   0:10   5.76% zfs
 1500 root          1  24    0 42248K  3768K pipewr  0   0:08   5.18% zfs

Here's what I set:

vfs.zfs.arc_max="4096M"
vfs.zfs.arc_min="1024M"
vfs.zfs.txg.timeout="3"
vfs.zfs.write_limit_override="512M"

I'm not seeing any obvious way to verify the write_limit_override setting -
it appears not to show up in sysctl output.

I'll wait for the current big transfer to finish and then I'll try it with
prefetch disabled too.

-- 
Mason Loring Bliss          mason at blisses.org          Ewige Blumenkraft!
awake ? sleep : random() & 2 ? dream : sleep; -- Hamlet, Act III, Scene I