DTrace to measure ZFS operations & latency

[Lacey Powers]

I put in a bug for this because the function is inlined and thus hidden
from dtrace. The patch hasn't been applied for several months.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200316

You could always custom compile to expose this like I did to try and debug
it for my own use with ZFS and PostgreSQL.

Hope that helps.

Regards,

Lacey
On Aug 20, 2015 10:48 AM, "Michael W. Lucas" <mwlucas at michaelwlucas.com>
wrote:

> Hi,
>
> I'm working on measuring the number & latency of async operations in
> ZFS. (Yes, this is still for the ZFS book.) There's a nice script at
> http://dtrace.org/blogs/ahl/2014/08/31/openzfs-tuning/, but it's
> illumos-specific. I try to run the script on last week's -current and
> get:
>
> # dtrace -s q.d zroot
> dtrace: failed to compile script q.d: line 4: probe description
> fbt::vdev_queue_max_async_writes:entry does not match any probes
>
> Any chance someone could help me out here?
>
> Thanks,
> ==ml
>
> PS: The script is:
>
> #pragma D option aggpack
> #pragma D option quiet
>
> fbt::vdev_queue_max_async_writes:entry
> {
>         self->spa = args[0];
>         }
>         fbt::vdev_queue_max_async_writes:return
>         /self->spa && self->spa->spa_name == $$1/
>         {
>                 @ = lquantize(args[1], 0, 30, 1);
>                 }
>
> tick-1s
> {
>         printa(@);
>                 clear(@);
>                 }
>
>
> --
> Michael W. Lucas  -  mwlucas at michaelwlucas.com, Twitter @mwlauthor
> http://www.MichaelWLucas.com/, http://blather.MichaelWLucas.com/
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