Performance of 4.x vs 5.x (Re: Lifetime of FreeBSD branches)

Kris Kennaway kris at
Tue May 24 12:54:19 PDT 2005

On Tue, May 24, 2005 at 09:41:29PM +0200, Max Laier wrote:
> On Monday 23 May 2005 23:21, Matthias Buelow wrote:
> > Kris Kennaway wrote:
> > > One thing that probably confuses and misleads a lot of people is when
> > > they build world or a kernel and notice that it's taking much longer
> > > than it did under 4.x, so they assume this means that 5.x is slower
> > > than 4.x.  It doesn't.  What it means is that 5.x and 4.x have
> > > different C compilers, and gcc 3.x is much slower at compiling code
> > > than gcc 2.x.  You have to be very careful to draw conclusions based
> > > on subjective assessments like this.
> >
> > Another thing might be that interactive response time seems to be worse.
> >  While I (or rather ports) unpack the firefox/thunderbird source, the
> > machine is pretty much bogged down (mouse cursor jumps around, audio
> > stutters...).  Haven't seen that on FreeBSD since the 386 days.
> I have seen this on my box.  Disabling one of the USB-ports solved the 
> problem.  I was seeing very high IRQ-rates.  Check $vmstat -i during the 
> process to see if you have abnormal high rate jumps.  It might be that we 
> must investigate some of our drivers to play nice with each other.

Actually, this is something that others have seen too (e.g. rwatson).
Specifically, if you have USB support enabled in your kernel and a USB
device shares an IRQ with some other device then every interrupt on
those devices causes USB to acquire Giant, significantly degrading
system performance.

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