Re: 2.6.12-mm1 boot failure on NUMA box.

Ingo Molnar
2005-06-25T09:10:18Z

* Martin J. Bligh <mbligh@mbligh.org> wrote:

> > (btw., if the TSC is that unreliable on numaq boxes, shouldnt we disable
> > it for userspace apps too? Or are those hangs purely kernel bugs? In
> > which case it might make sense to debug those a bit more - large-scale
> > TSC unsyncedness is something that could slip in on other hardware too.)
>
> Well it reads reliably. it just reliably reads utter random crap
> (well, across CPUs). Not many things read tsc from userspace, and it
> won't hang I guess .... depends what their expecations are. I do like
> gettimeofday not to go backwards though - that tends to bugger things
> up ;-)

the patch only adds the TSC back for purposes of sched_clock() (whose
call sites are robust against cross-CPU migration) - gettimeofday() is
still using the PIT or HPET.

but i intended this to be an problem-free change - if it causes any
problems i'll switch the code to use gettimeofday() and not the
[thus-]lower-accuracy sched_clock().

Ingo