RFC: Adding a hw.features[2] sysctl

Nathan Lay nslay at comcast.net
Sun Jan 13 18:11:49 PST 2008


Igor Mozolevsky wrote:
> On 13/01/2008, Peter Jeremy <peterjeremy at optushome.com.au> wrote:
>
>   
>> IMHO, no.  Virtually all similar FreeBSD information is exported via
>> sysctl and this sort of information fits neatly into the existing
>> MIB tree as either dev.cpu.N.features or hw.cpu.features
>>     
>
> /dev/sndstat?
>
> If it's in /dev you can do neat tricks like ioctl-ing queries (like
> ioctl(/dev/cpuinfo, CINFOCTL_HAS_FEATURES, CINFO_SSE3|CINFO_SSSE3))
> instead of having *every* app parse the result of a sysctl; most of
> the time you'd only want to check for specific feature , it's much
> easier to do an ioctl that returns a boolean.
>
> Igor
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>   
Or perhaps, create an ioctl that returns a bitmask of all available CPU 
features.  This way, only one ioctl() call is necessary and allows 
programs to query any and all features in an inexpensive way.  Calling 
ioctl() for each feature query is comparably more expensive.

Best Regards,
Nathan Lay


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