Re: CVS commit: src/sys/arch

[Chuck Silvers <chuq%chuq.com@localhost>]

On Mon, Dec 05, 2011 at 12:29:25AM +0000, Mindaugas Rasiukevicius wrote:
> "Chuck Silvers" <chs%netbsd.org@localhost> wrote:
> > Module Name:        src
> > Committed By:       chs
> > Date:               Sun Dec  4 16:24:13 UTC 2011
> > 
> > Modified Files:
> >     src/sys/arch/amd64/amd64: locore.S machdep.c
> >     src/sys/arch/amd64/include: types.h
> >     src/sys/arch/x86/include: pmap.h
> >     src/sys/arch/x86/x86: pmap.c
> > 
> > Log Message:
> > map all of physical memory using large pages.
> > ported from openbsd years ago by Murray Armfield,
> > updated for changes since then by me.
> 
> This is cool, thanks!  Can you add an entry to src/doc/CHANGES?  Also,
> just wondering - did you try any benchmarks?  I would expect reasonable
> improvement.

does it really make sense to list incremental performance improvements there?
I can add it if folks want, but we don't tend to document misc performance
improvements that have no API impact outside the kernel.

as for how much it helps, on a 12-CPU box "build.sh release" is about 2.5%
faster.  if I enable __HAVE_CPU_UAREA_ROUTINES so that uareas are also
accessed this way that gives an additional 0.5% speedup.

coincidentally, this almost exactly compensates for the performance hit
of enabling DIAGNOSTIC.

-Chuck