Re: Initial 6.1 questions

On Mon, Jun 12, 2006 at 09:08:12PM +0100, Robert Watson wrote:
On Mon, 12 Jun 2006, Scott Long wrote:

I run a number of high-load production systems that do a lot of network
and filesystem activity, all with HZ set to 100. It has also been shown
in the past that certain things in the network area where not fixed to
deal with a high HZ value, so it's possible that it's even more
stable/reliable with an HZ value of 100.

My personal opinion is that HZ should gop back down to 100 in 7-CURRENT
immediately, and only be incremented back up when/if it's proven to be the
right thing to do. And, I say that as someone who (errantly) pushed for
the increase to 1000 several years ago.

I think it's probably a good idea to do it sooner rather than later. It
may slightly negatively impact some services that rely on frequent timers
to do things like retransmit timing and the like. But I haven't done any
measurements.

As you know, but for the benefit of the list, restoring HZ=100 is
often an important performance tweak on SMP systems with many CPUs
because of all the sched_lock activity from statclock/hardclock, which
scales with HZ and NCPUS.

Kris

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