ZFS patches

[Pawel Jakub Dawidek]

On Wed, May 30, 2012 at 05:32:34PM -0700, Chuck Silvers wrote:
> we only have a few changes to ZFS itself, and now that I look I see that
> you've found one of them independently (r230256).
> 
> the other ones are:
> 
>  - improve performance of booting from a ZFS root under ESXi.
>    previously this would sit there for about 5 minutes before even
>    starting to load the kernel.  the problem is that the ZFS pool-discovery
>    code opens every possible GPT partition looking for pools, and it rereads
>    the GPT each time, one sector at a time.  we changed the GPT code to
>    read the whole GPT in one shot, which reduced the delay to almost nothing.
>    I remember seeing some discussion about a PR on this topic some time back
>    but I don't know if any fix was ever applied and I don't see the PR now.
>    as I recall, the proposal in that discussion was to improve the boot code
>    caching so that it wouldn't reread the GPT at all, which I imagine would
>    work just as well as what we did.
>    (hmm, this isn't actually a change to ZFS either.)

The problem I remember with this code was that it checked 128 partitions
for every single disk in a brute-force fasion in hope that maybe there
are no p3-p110 partitions, but maybe there is p111 one.

Easy (but not ideal) solution to this was to stop scanning partitions
when 3 in a row don't exist. Ideal solution was to teach the code to
actually look into partition table and trying only those partitions that
really exist.

I haven't looked closely at your patch yet, though.

>  - make zfs_resilver_delay and zfs_resilver_min_time_ms tunable via sysctl.

I have a bigger patch for this too:

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

The reason I didn't commit this patch yet is that some of those values
can be safely modified after boot can could be made CTLFLAG_RW like
maybe the two you convered.

If you would like to analyse them and see which are safe to be made RW
that would be great.

-- 
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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