On Thu, Oct 04, 2007 at 08:21:59PM +0200, Andi Kleen wrote: > On Thursday 04 October 2007 20:10:44 Dave Jones wrote: > > On Thu, Oct 04, 2007 at 07:53:16PM +0200, Andi Kleen wrote: > > > > > > > The only vendor that ever implemented OOSTOREs was Centaur, and they > > > > only did in the Winchip generation of the CPUs. When they dropped it > > > > from the C3, I asked whether they intended to bring it back, and the > > > > answer was "extremely unlikely". > > > > > > > > > > Do you know if it made a big performance difference? > > > > On the winchip, it was a huge win. I can't remember exact numbers, > > but pretty much every benchmark I threw at it at the time showed > > significant improvement. > > Significant as in >10%?
"Worth about 10-20% performance" according to the 2.4.18pre9-ac4 release notes: http://www.linuxtoday.com/news_story.php3?ltsn=2002-02-14-015-20-NW-KN > > > But yes we should probably just remove this special case to make > > > maintenance easier. > > It's CONFIG_SMP anyway, which none of the winchips were. > > It's not. You're right it isn't now, but Nicks patch seems to change it so that it is. ... #ifdef CONFIG_SMP #define smp_mb() mb() #define smp_rmb() rmb() -#define smp_wmb() wmb() +#ifdef CONFIG_X86_OOSTORE +# define smp_wmb() wmb() +#else +# define smp_wmb() barrier() +#endif > And we need memory barriers even without SMP > when talking to device drivers. Only the smp_*b()s get noped > on UP. Good point. Dave -- http://www.codemonkey.org.uk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
