FreeBSD 10.1 Memory Exhaustion

[Matthew Seaman]

On 07/13/15 12:58, Karl Denninger wrote:
> Put this on your box and see if the problem goes away.... :-)
> 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594
> 
> The 2015-02-10 refactor will apply against 10.1-STABLE and 10.2-PRE (the
> latter will give you a 10-line fuzz in one block but applies and works.)
> 
> I've been unable to provoke misbehavior with this patch in and I run a
> cron job that does auto-snapshotting.  There are others that have run
> this patch with similarly positive results.

I know that you, Karl, and a number of others have been advocating to
get this patch set committed.  Having now personally run into the sort
of problems that this addresses I can say that I would very much like to
see this go in.  Conditional of course on this actually solving the
problems I and others have been experiencing without introducing
significant regressions elsewhere. It's only had a day's testing from me
so far, but it's looking good.  If it survives a week without the system
locking up, I'll be convinced.

I also know that some of the most experienced ZFS developers are
cautious about applying this patchset, and I do not doubt that they have
good reason to think so.

What I wonder is could it be possible to generate some sort of
regression tests where

   * The memory exhaustion effect or equivalent memory pressures can be
     triggered at will
   * The test doesn't require unfeasibly large resources to run
   * The behaviour provides a good model for real-world deployments

Maybe these tests would be too large-scale to run every day in Jenkins,
but having them available as part of, say, the release process, seems
like a no-brainer to me.

ZFS is one of FreeBSD's big selling points, and not having it work
reliably at scale is an embarrassment, to say the least.

	Cheers,

	Matthew



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