Date: Fri, 18 Mar 2011 12:38:11 -0400 From: Jung-uk Kim <jkim@FreeBSD.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, Bruce Evans <brde@optusnet.com.au>, Andriy Gapon <avg@freebsd.org>, Maxim Dounin <mdounin@mdounin.ru> Subject: Re: get_cyclecount(9) deprecation Message-ID: <201103181238.14793.jkim@FreeBSD.org> In-Reply-To: <20110318161524.GC78089@deviant.kiev.zoral.com.ua> References: <201103171436.22283.jkim@FreeBSD.org> <4D837F7F.2060403@freebsd.org> <20110318161524.GC78089@deviant.kiev.zoral.com.ua>
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On Friday 18 March 2011 12:15 pm, Kostik Belousov wrote: > On Fri, Mar 18, 2011 at 05:51:27PM +0200, Andriy Gapon wrote: > > on 18/03/2011 15:56 Kostik Belousov said the following: > > > On Fri, Mar 18, 2011 at 05:26:53PM +1100, Bruce Evans wrote: > > > ... > > > > > >> - set cputicker() has some design bugs. It assumes that the > > >> tick frequency is the same across all CPUs, but the TSC is > > >> per-CPU. I have an old SMP system with CPUs of different > > >> frequency that can demonstrate bugs from this. > > > > > > We definitely do not support configurations with different > > > models of CPUs in SMP, this is what Simmetric is about. > > > Different as in frequency or stepping. > > > > Are there any fundamental reasons for us to not support that > > configuration in situations where hardware and BIOS (in x86 case) > > happen to support it? > > > > I am personally more interested in non-uniform topologies like > > one package having two cores and another having four. > > We do not handle CPU errata/quirks individually per-core. I think > that we assume that all cores have the same stepping and thus > require the same workarounds, if any, as BSP. Also, I think tsc > calibration is done only on BSP, but I may be wrong there. Yeah, it is just sad but that's what we do now. Just for per-CPU ticker, however, it won't be too hard, though. Jung-uk Kim
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