That looks fine.  I don't have any experience with how devices respond to
concurrent TRIM commands, so I would defer to you on what that
trim_max_active should be.

I could see arguments either way on whether TRIM should be higher or lower
priority than SCRUB, but in practice it doesn't matter; the priority only
comes into play once you have zfs_vdev_max_active total i/os queued to the
device.  By default this is larger than the sum of all queue's
max_active's, so unless zfs_vdev_max_active is lowered it is not possible
for the priority to matter.

--matt


On Sat, Nov 30, 2013 at 7:13 AM, Andriy Gapon <[email protected]> wrote:

> [resending with CC fixed]
>
> Matt,
>
> as you most likely know, ZFS/FreeBSD already has ability to use TRIM
> command
> with disks that support it.
> As the command can be quite slow and it is a maintenance kind of command,
> it
> makes sense to assign a very low priority to it.
>
> I've come up with the following change that introduces a new priority for
> the
> TRIM zios:
> http://people.freebsd.org/~avg/zfs-trim-priority.diff
> To be honest, this change actually attempts to restore what we already had
> in
> FreeBSD before I merged your write throttle & i/o scheduler performance
> work.
>
> Could you please review the change?
> I am not sure if I correctly translated my intent to the min_active and
> max_active values.  I will greatly appreciate your help with these.
>
> Thank you!
> --
> Andriy Gapon
>
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