Re: cache sync on zvols - other problems?

[Greg Troxel <gdt%lexort.com@localhost>]

Greg Troxel <gdt%lexort.com@localhost> writes:

>   a n11-amd64 (11 means current) is ok, but after overnight, it is very
>   very sluggish in disk io and the dom0's top shows
>        0 root      96    0     0K   71M CPU/11    408:43 99.76% 99.76% [system]
>   and this does not seem to recover

This is apparently all because I had too many printfs about ARC
management, and they were too often.  I commented out all the ones that
fired under load, and things are vastly better.

I am therefore going to re-activate the pullup request to 10.   Please
feel free to test if you think you might be adversely affected.


> Can anyone explain when xen decides to call DIOCCACHESYNC?  Is that when
> there is a corresponding cache flush disk command from the domU?

still a valid question :-)

> My guess is that cache flushing is pretty expensive and that a scheme
> that does flushes when soundness says is going to be trouble, but I
> really am unclear on the details.

I still believe this.