Re: HMP scheduling on FreeBSD

On 1/15/26 20:37, Adrian Chadd wrote:
> . . .
> 
> There are systems shipping right now with three types of AP cores on
> one die. I've had to debug systems in the past with the big/little
> cores having
> different cache line sizes. It's a mess. Manufacturers will do
> whatever they can and patch linux to do whatever they need to. :-)
> 
> I've also seen Linux software literally pass the output of "cat
> /proc/cpuinfo" to figure out this mess and then will do utterly
> baffling things
> like decide upon cache management, cpu workload scheduling, etc based
> on matching on the contents of said /proc/cpuinfo.

Hmm. As I remember, possibly incorrectly, I once had to look up how
something worked for /proc/cpuinfo and it turned out what I was looking
for was something that was not (yet?) set up to be handled. So
/proc/cpuinfo reported the feature as not available when it fact it was
indicated as possible by the original bits: more of an 'are things ready
for this to be used' than a 'this is what the original bits report about
the core'. I've no clue how common such may be.

> 
> I also believe there are some feature differences between the Intel
> power/efficiency cores? I haven't dug too deeply into it.
> 
> That's why I'd like to figure out how to describe to userland and the
> rest of the kernel all these bits and pieces.
> The HMP stuff is a good move towards the scheduler side of stuff but I
> really don't want it wrapped up in some
> "the kernel will just do it magically" without letting some policy
> stuff be configured.
> 
> 
> -adrian
> 
> 


-- 
===
Mark Millard
marklmi at yahoo.com