Re: 2.6.21-rc3-mm1 RSDL results

[Matt Mackall <mpm@selenic.com>]

On Sat, Mar 10, 2007 at 09:18:05AM +1100, Con Kolivas wrote:
> On Saturday 10 March 2007 08:57, Con Kolivas wrote:
> > On Saturday 10 March 2007 08:39, Matt Mackall wrote:
> > > On Sat, Mar 10, 2007 at 08:19:18AM +1100, Con Kolivas wrote:
> > > > On Saturday 10 March 2007 08:07, Con Kolivas wrote:
> > > > > On Saturday 10 March 2007 07:46, Matt Mackall wrote:
> > > > > > My suspicion is the problem lies in giving too much quanta to
> > > > > > newly-started processes.
> > > > >
> > > > > Ah that's some nice detective work there. Mainline does some rather
> > > > > complex accounting on sched_fork including (possibly) a whole timer
> > > > > tick which rsdl does not do. make forks off continuously so what you
> > > > > say may well be correct. I'll see if I can try to revert to the
> > > > > mainline behaviour in sched_fork (which was obviously there for a
> > > > > reason).
> > > >
> > > > Wow! Thanks Matt. You've found a real bug too. This seems to fix the
> > > > qemu misbehaviour and bitmap errors so far too! Now can you please try
> > > > this to see if it fixes your problem?
> > >
> > > Sorry, it's about the same. I now suspect an accounting glitch involving
> > > pipe wake-ups.
> > >
> > > 5x memload: good
> > > 5x execload: good
> > > 5x forkload: good
> > > 5 parallel makes: mostly good
> > > make -j 5: bad
> > >
> > > So what's different between makes in parallel and make -j 5? Make's
> > > job server uses pipe I/O to control how many jobs are running.
> >
> > Hmm it must be those deep pipes again then. I removed any quirks testing
> > for those from mainline as I suspected it would be ok. Guess I"m wrong.
> 
> I shouldn't blame this straight up though if NO_HZ makes it better. Something 
> else is going wrong... wtf though?

Just so we're clear, dynticks has only 'fixed' the single non-parallel
make load so far.

-- 
Mathematics is the supreme nostalgia of our time.