Messages in this thread |  | | | Date | Thu, 12 Nov 2009 09:13:17 +0100 | | From | Ingo Molnar <> | | Subject | Re: [PATCH RFC] x86: fix confusing name of /proc/cpuinfo "ht" flag |
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* H. Peter Anvin <hpa@zytor.com> wrote:
> On 11/11/2009 10:59 PM, Ingo Molnar wrote: > > > > * Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> wrote: > > > >> "ht" flag indicates only ability to detect siblings not HT presence > >> itself. > >> > >> Inspired by: > >> http://www.codemonkey.org.uk/2009/11/10/common-hyperthreading-misconception/ > > > > i think instead of changing 'ht' to 'ht_detect', it would be even > > more intuitive to only expose the 'ht' flag if the ht-detect > > capability is there _and_ if the number of siblings is 2 or more. > > > > That way we dont change it - we just 'hide' the 'ht' string on the > > category of systems that can enumerate HT via the CPUID but dont > > actually have HyperThreading. > > /proc/cpuinfo is a user-space visible ABI. Changing it is bad > chicken.
Almost ... something is only an ABI if an actual application relies on the 'ht' flag being there on non-hyperthreading CPUs. We dont know whether there's any, but the likelyhood looks pretty low. Could park it a branch for some time to see whether anything trips up.
Ingo
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