From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: Ulrich Drepper <drepper-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: CPUID emulation
Date: Thu, 31 May 2007 18:12:35 -0700 [thread overview]
Message-ID: <465F7283.6080309@zytor.com> (raw)
In-Reply-To: <465F145F.5040003-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Ulrich Drepper wrote:
> Stephane Eranian wrote:
>> They use cpuid. I expect more and more applications/OS will rely on
>> performance counters to boost performance at runtime.
>
> That's a definitive fact. ld.so for the longest time selects special
> DSOs to load automatically based on the data. String functions are
> optimized to take cache sizes into account. That info comes from cpuid
> as well (at least on Intel CPUs). It's crucial to get info based on the
> current CPU.
If you want migration, it's crucial that you get information that is
appropriate for the baseline you want to emulate. Optimizations is one
thing, but if you start using SSE-12 instructions when the underlying
CPU only supports SSE-8, you're horked.
-hpa
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prev parent reply other threads:[~2007-06-01 1:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-31 8:20 CPUID emulation Stephane Eranian
[not found] ` <20070531082006.GB22798-HU54gidqsKnWxDs0y9d3MAC/G2K4zDHf@public.gmane.org>
2007-05-31 8:39 ` Avi Kivity
[not found] ` <465E89A8.9020201-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2007-05-31 11:29 ` Stephane Eranian
[not found] ` <20070531112906.GC22798-HU54gidqsKnWxDs0y9d3MAC/G2K4zDHf@public.gmane.org>
2007-05-31 11:35 ` Avi Kivity
[not found] ` <465EB310.7080402-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2007-05-31 11:44 ` Stephane Eranian
[not found] ` <20070531114447.GF22798-HU54gidqsKnWxDs0y9d3MAC/G2K4zDHf@public.gmane.org>
2007-05-31 11:52 ` Avi Kivity
[not found] ` <465EB6E5.7000000-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2007-05-31 11:58 ` Stephane Eranian
[not found] ` <20070531115841.GG22798-HU54gidqsKnWxDs0y9d3MAC/G2K4zDHf@public.gmane.org>
2007-05-31 15:12 ` Troy Benjegerdes
[not found] ` <20070531151244.GC6474-na1kE3HDu0idQnJuSAr7PQ@public.gmane.org>
2007-05-31 15:38 ` ron minnich
2007-05-31 18:30 ` Ulrich Drepper
[not found] ` <465F145F.5040003-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2007-06-01 1:12 ` H. Peter Anvin [this message]
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