[zfs-devel] Ping: reasoning in module/zfs/zfs_ctldir.c

u-odpp at aetey.se u-odpp at aetey.se
Thu Oct 13 03:18:23 EDT 2016


On Wed, Oct 12, 2016 at 03:13:55PM -0600, Andreas Dilger wrote:
> I think one of the major technical limitations of ZFS on 32-bit platforms was the limited vmalloc address space, since ZFS used vmalloc heavily for large data block buffers.
> 
> The ABD patches (not yet landed for 0.7.0) remove the need for vmalloc in the IO path, so ZFS should be much more usable on 32-bit platforms than before.

That's a great news.

> ZFS itself works fine with 32-bit systems (AFAIK, based on comments for BSD), so I don't think there is a fundamental objection to it, just a shortcoming in the Linux kernel that is making it more difficult, and a general lack of people who are using 32-bit CPUs these days. 

I ran ZFS on BSD on 32-bit, memory constrained systems and
thankfully did not run into any remarkable issues, given reasonable tuning.

> If this is a area of interest to you, I would strongly recommend that you get the latest version of the ABD patch and test it on your platform and provide feedback to the developers. I suspect they will be generally helpful in response to any issues you find, but don't expect others to do extra work on a "fringe" platform if you aren't willing to put in some effort there yourself.

I have limited margins for following moving targets like development
patches but thanks for the suggestion, I will try to.

> If this is of real interest to you (e.g. you depend on this working for some platform you support), you could even register a buildbot for your platform and run extended testing to ensure that regressions are not introduced with new patches. 

The possibility to combine ZFS and a 32-bit kernel spares quite a lot
of trouble, so it is certainly worth an effort. I'll do what I can.

Thanks Andreas.

Regards,
Rune



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