cvs commit: src/sys/amd64/conf GENERIC

[John Baldwin]

On Monday 14 June 2004 02:21 pm, Robert Watson wrote:
> On Mon, 14 Jun 2004, John Baldwin wrote:
> > On Sunday 13 June 2004 07:03 pm, David E. O'Brien wrote:
> > > obrien      2004-06-13 23:03:57 UTC
> > >
> > >   FreeBSD src repository
> > >
> > >   Modified files:
> > >     sys/amd64/conf       GENERIC
> > >   Log:
> > >   The majority of FreeBSD/amd64 machines are SMP, so use
> > > ADAPTIVE_MUTEXES by default to improve performance.
> >
> > We don't know if it improves performance yet. :)
>
> Yeah, as I was mentioning to David over the weekend, it's believed to help
> performance anecdotally in a number of interesting cases, and if we can
> show it helps in a majority of interesting cases (and doesn't
> substantially hurt the others) then I think this should actually be in
> GENERIC across all platforms, not just amd64.  I also found I
> misunderstood his commit message as it seems to suggest it helps SMP at
> the cost of UP, but in fact does not say that.
>
> Kris reported that he experienced some apparent hangs related to running
> with ADAPTIVE_MUTEXES and we should resolve if it was actually the cause
> or whether it just triggered an existing race.

I'm betting it is just triggering a race.  When I first did the adaptive 
mutexes I stress tested it (-j <bignum> buildworld loops) on an ultra60, an 
alpha ds20, and a quad pii-xeon w/o any lockups.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org