Re: Dom0 starvs DomU

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sun, Nov 15, 2015 at 03:08:28PM +0100, dieter roelants wrote:
> On Sun, 15 Nov 2015 14:16:46 +0100
> tg%gmplib.org@localhost (Torbjörn Granlund) wrote:
> 
> > 
> > Please understand that I have yet to hit a (NetBSD release x Xen release
> > x configuration) where compiling in Dom0 does not make DomU disk
> > operations outragously slow.
> > 
> > The underlying disk speed does not seem to be a factor.  (I used to have
> > spinning rust, now most systems run top-of-the-line SSDs.)
> > 
> > Instead of asking me to try more configurations, please consider trying
> > to reproduce this.
> 
> A possibly interesting datapoint; I have recently seen (multiple times)
> similar symptoms but under different circumstances. The culprit in my
> case was a misbehaving web application of which the backend crashed and
> the javascript frontend kept on constantly sending requests. This
> resulted in firefox hogging the CPU in dom0 and also in ssh sessions to
> the domU's being barely responsive. So, no real I/O involved here
> (although I guess network access may have been responsible too).

It would be interesting to know if the CPU time is spent in
kernel or userland. The dom0's CPU being busy in kernel could indeed explain
it.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--