Re: ZFS patches.

Pawel Jakub Dawidek wrote:
> Hi.
> 
> 	http://people.freebsd.org/~pjd/patches/zfs_20080727.patch.bz2
> 
> The patch above contains the most recent ZFS version that could be found
> in OpenSolaris as of today. Apart for large amount of new functionality,
> I belive there are many stability (and also performance) improvements
> compared to the version from the base system.
> 
> Check out OpenSolaris website to find out the differences between base
> system version and patch version.
> 
> Please test, test, test. If I get enough positive feedback, I may be
> able to squeeze it into 7.1-RELEASE, but this might be hard.

I currently don't have high-end (4 CPU+) AMD64 machines to test, but 
with 1 CPU i386 virtual machine in VMWare, with 1 GB of memory, 
kmem_size=kmem_size_max=512M and no other tuning, with latest zpool 
format (11) it took about 15 minutes to get a "kmem_map too small" panic 
on a mixed load (buildkernel + blogbench + bonnie++).

I've then tried the same load on the "real" hardware, 2 CPU, 2 GB 
memory, kmem_size=kmem_size_max=512M, and no other tuning, with the 
older zpool format (6) i get the same panic, though it takes about twice 
as long to happen.

In both cases, iostat was running and I noticed there's about 30 seconds 
of complete inactivity (CPU 100% idle, no IO on any drives) just before 
the panic. Locking issue? In the second case I was also monitoring the 
system more closely and before the inactivity period the IO bandwidth 
gets really slow, considering the type of load I'm generating: cca 2 
MB/s, with all tasks except bonnnie++ stopped (SIGSTOP), and bonnie++ 
generating large-block writes. This is what provoked the panic in the 
second case.

Core dumps are available, as always.

But, overall, I see a definite improvement here. Before the new patch I 
could panic the machine within a minute and now it can survive much more 
beating. If the other problems (deadlocks) are solved, I'd say it's 
worth the effort to get it in 7.1 - considering what's in 7.0, any 
improvement helps.