cvs commit: src/sys/amd64/conf GENERIC

[John Baldwin]

On Thursday 14 December 2006 10:55, David O'Brien wrote:
> On Wed, Dec 13, 2006 at 08:13:24PM -0800, mjacob at freebsd.org wrote:
> > Secondly, I would *like* to have SMP on as a default in RELENG_6 for 
> > amd64, as it would avoid doing what I've done twice already- fresh 
> > sysinstall may or may not have installed an SMP kernel but going off and 
> > building GENERIC then lost me my SMP. It's sort a violation of POLA.
> 
> Rather close what happened to me and what lead to the commit.

How long did it take you to notice and fix it?  Right now the out of box 
experience is optimal for both UP and SMP boxes.  People who want to go 
compile their own kernel can be expected to have sufficient clue to either 1) 
notice up front that SMP isn't in their kernel config, or 2) notice right 
after they boot and fix it then.  Neither one would consitute what I would 
call a "major" headache.
 
> On Wed, Dec 13, 2006 at 10:17:02PM -0700, Scott Long wrote:
> > mjacob at freebsd.org wrote:
> > > Scott Long wrote:
> > > > There wasn't a full switchover to SMP at 6.0 because an SMP kernel
> > > > on a UP system incurs a measurable runtime overhead, and we wanted
> > > > to present a system that showed the best of FreeBSD to people who
> > > > wanted to run it
> 
> Then why is sparc64's GENERIC kernel SMP in RELENG_6?

It doesn't have the same measurable impact on UP machines to run an SMP 
kernel.
 
> > > But David's point is that most AMD64 boxes *are* SMP, not UP.  Is
> > > that wrong?
> > 
> > 1. There are plenty of single core Opterons and Athlon64 chips still
> > in service.
> 
> A few points:
> 
> * FreeBSD is predominately a server OS, not home desktop OS.
> 
> * Practically all single core Opteron's are used in multi-socket systems.
> There are very, very few Opteron single socket, single core Opteron's in
> service as there are only a very small handful of single socket 940-pin
> motherboards.
> 
> * Most Athlon64 single-core CPU's are run in 32-bit "i386" mode.
> FreeBSD/i386 isn't the platform I (and presumably Matt) are talking
> about.
> 
> > Maybe AMD sells more SMP systems now than UP systems, but their prior
> > sales of UP systems didn't magically disappear overnight.
> 
> This is not an AMD-only situation.
> 
> Intel has been selling dual-core processors since 18 April 2005, and now
> sells quad-core processors.  Also, Intel kept Long Model (i.e., EM64T)
> to the server/workstation segment until its dual-core processors.  For
> instance, most Intel laptops cannot run FreeBSD/AMD64.

And right now the out of the box experience for users after an install is that 
all those systems will use an SMP enabled kernel.

-- 
John Baldwin