[coyotos-dev] EROS small processes

[Jonathan S. Shapiro]

Yuck.

Thanks.

On Tue, 2007-01-23 at 14:58 -0500, Eric Northup wrote:
> Jonathan S. Shapiro wrote:
> > On Tue, 2007-01-23 at 13:21 -0500, Eric Northup wrote:
> >> Jonathan S. Shapiro wrote:
> >>> Small spaces are a nuisance to implement. A while back AMD implemented a
> >>> mechanism that significantly improved TLB flush performance, and in
> >>> later processors Intel was forced to follow AMD's lead to keep
> >>> competitive. It isn't clear how important the small space optimization
> >>> is for these newer processors.
> >> Due to errata and its general lack of improvement for common...
> > 
> > Eric: can you provide pointers to the relevant errata?
> > 
> 
> Quoting AMD document 25759 "Revision Guide for AMD Athlon™ 64 and AMD 
> Opteron™ Processors" (Rev. 3.69 September 2006 ), the relevant one for 
> production processors is #122:
> 
> > TLB Flush Filter May Cause Coherency Problem in
> > Multiprocessor Systems
> > Description
> > Under highly specific internal timing conditions in a multiprocessor configuration, coherency
> > problems may arise between the page tables in memory and the translations stored in the on-chip
> > TLBs. This can result in the possible use of stale translations even after software has performed a
> > TLB flush.
> > Potential Effect on System
> > Unpredictable system failure. This scenario has only been observed in a highly randomized synthetic
> > stress test.
> > Suggested Workaround
> > In multiprocessor or multicore systems, disable the TLB flush filter by setting HWCR.FFDIS (bit 6 of
> > MSR 0xC001_0015).
> > Fix Planned
> > No
> 
> I haven't checked whether single-processor AMD64 systems enable it or 
> not, since all I have are dual-core.
> 
> -Eric
> _______________________________________________
> coyotos-dev mailing list
> coyotos-dev at smtp.coyotos.org
> http://www.coyotos.org/mailman/listinfo/coyotos-dev
-- 
Jonathan S. Shapiro, Ph.D.
Managing Director
The EROS Group, LLC
+1 443 927 1719 x5100