HZ=1000 on slow CPUs considered harmful?
chrcoluk at gmail.com
Wed Feb 23 14:04:03 GMT 2005
I have noticed issues with HZ=1000 on a celeron 2ghz and a AMD64
3.2ghz, both caused problems with glftpd app and I had to recompile
kernel back to default HZ=100 to fix, I have also noticed HZ=1000 add
latency on my celeron box.
On Tue, 22 Feb 2005 14:00:09 -0800, Kevin Oberman <oberman at es.net> wrote:
> > Date: Tue, 22 Feb 2005 22:48:21 +0100
> > From: cpghost at cordula.ws
> > On Tue, Feb 22, 2005 at 07:56:03PM +0000, Robert Watson wrote:
> > > In 6-CURRENT, HZ is 1000 for amd64, i386, and ia64, but 100 for other
> > > platforms (i.e., ppc, arm, and alpha). I'm not opposed to merging the HZ
> > > change to RELENG_5 at some point, but given that occasional nits, such as
> > > the TCP nit, are turning up, I think it's worth waiting until after 5.4.
> > Wouldn't that be a problem for slow CPUs like VIA C3 (EPIA) or GEODE
> > (Soekris)? For fast CPUs, it's not that much overhead, but for slow
> > CPUs?
> > Can HZ remain user-configurable?
> > > Robert N M Watson
> > Thanks,
> > -cpghost.
> > --
> > Cordula's Web. http://www.cordula.ws/
> As far as I know, no one is talking about removing the knob. I believe
> the issue is the default value changing from 100 to 1000. There are many
> boxes that would not be very happy with 1000. I'm sure that there are
> many 75 MHz Pentiums and 66 MHz 486s still running FreeBSD and even running
> R. Kevin Oberman, Network Engineer
> Energy Sciences Network (ESnet)
> Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
> E-mail: oberman at es.net Phone: +1 510 486-8634
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