--On 13 September 2011 14:05:41 +0200 Paolo Bonzini<pbonzini-H+wXaHxf7aLQT0dZR+AlfA@...953...>
wrote:
I see you've got support for NBD_TIMEOUT in your patch set too.
That might be better broken out.
It's just ioctl_cmd_to_ascii.
doh. That's what I get for reading too fast.
I get the feeling patch 3/4 is going not going to get applied.
I should really fix nbd-client so it doesn't need this.
FWIW I've seen multiple reports of getting better performance _without_
NONROT, but I don't see anything particularly bad in that patch. Flags
are just a hint, you can always ignore them.
Indeed.
The case where you want NONROT set is where the elevator of the server is
likely to outperform the client, and there is very little latency between
the two ends (i.e. client elevator merges gain nothing). Small client
VMs are an example.
The case where you want NONROT unset is where the client elevator is useful
(e.g. big memory server) and where the server will heavily benefit from
adjacent requests being merged, e.g. where there is a caching strategy
which is heavily localised.
Personally, I think NONROT unset is a better default, but then I haven't
done lots of timings. I would be interested to know how we came upon
the current default though.
Out of interest, what kernel(s) have you compile-tested these
against? I'd quite like to get them into my standalone module
tree (which is far far easier to test against).
3.0.3
OK - I think my tree is based on 2.6.32, so I may have a little
work to do.