[CFR] Tunables for scrub and resilver

[Pawel Jakub Dawidek]

On Sun, Jul 01, 2012 at 05:48:16PM +0200, Martin Matuska wrote:
> Hi,
> 
> I would like to hear your opinion on the attached patch to add scrub and
> resilver tunables.
> This way users can add more priority to scrub and resilver (make it
> faster) at cost of other I/O etc.
> 
> On-line version of the patch:
> http://people.freebsd.org/~mm/patches/zfs/dsl_scan.patch
> 
> The patch adds tuning for all of the dsl_scan.c tunables, as available
> in illumos.
> zfs_resilver_delay and zfs_scrub_delay (resulting in scan_delay) need to
> be non-negative, otherwise we trigger a kernel assert in pause().
> Other values are used for timer comparsions and should be safe even if
> negative (resulting behavior equals a value of zero).

I had similar patch for some time now:

	http://people.freebsd.org/~pjd/patches/dsl_scan.c.patch

The only reason I haven't committed it was that I wasn't sure with
variables can be safely modified at run-time. If you did the audit and
you are sure we can make them RW, then I'm fine with the patch (except
for style issues mentioned below).

> +SYSCTL_INT(_vfs_zfs, OID_AUTO, top_maxinflight, CTLFLAG_RW,
> +	&zfs_top_maxinflight, 0, "Maximum I/Os per top-level vdev");

Should be four spaces instead of tab.

> -			delay(scan_delay);
> +			delay(MAX(scan_delay,0));

Missing space before comma.

Although maybe we should make it unsigned and use SYSCTL_UINT()?

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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