Messages in this thread |  | | Date | Thu, 7 Dec 2000 17:07:07 +0100 (MET) | From | "Maciej W. Rozycki" <> | Subject | Re: Microsecond accuracy |
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On 7 Dec 2000, H. Peter Anvin wrote:
> Unfortunately the most important instance of the in-kernel flag -- the > global one in the somewhat misnamed boot_cpu_data.x86_features -- > isn't actually readable in the /proc/cpuinfo file. It is perfectly > possible (e.g. the "notsc" option) for ALL the CPUs to report this > capability, but the global capability to still be off.
Hmm, I recall I implemented and explicitly verified switching the /proc/cpuinfo "tsc" flag (as well as the userland access to the TSC) off when I wrote the code to handle the "notsc" option. Has it changed since then? I recall you modified the code a bit -- I looked at the changes then but I was pretty confident the semantics was preserved.
There is no possibility to have TSC and non-TSC chips mixed in a single SMP system (due to existing hardware, even though it's possible in theory), so there is no problem with such an assymetry. Either all chips have the "tsc" flag in /proc/cpuinfo on or off.
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
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