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Date: Thu, 4 Oct 2007 20:21:59 +0200 From: Andi Kleen <ak@...e.de> To: Dave Jones <davej@...hat.com> Cc: Nick Piggin <npiggin@...e.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [rfc][patch 2/3] x86: fix IO write barriers 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%? > > 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. And we need memory barriers even without SMP when talking to device drivers. Only the smp_*b()s get noped on UP. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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