Re: port-i386/38634: x86 kernels no longer produces information about cpus

[Chris Gilbert <chris%dokein.co.uk@localhost>]

Andrew Doran wrote:
> The following reply was made to PR port-i386/38634; it has been noted by 
> GNATS.
> 
> From: Andrew Doran <ad%netbsd.org@localhost>
> To: gnats-bugs%NetBSD.org@localhost
> Cc: 
> Subject: Re: port-i386/38634: x86 kernels no longer produces information 
> about cpus
> Date: Mon, 12 May 2008 13:39:51 +0100
> 
>  On Mon, May 12, 2008 at 11:20:01AM +0000, chris%NetBSD.org@localhost wrote:
>  
>  > dmesg used to contain information about cache sizes and feature flags for 
> cpus (even if it was wrong for non-cpu0s).
>  > 
>  > This information has been completely stripped and appears to have moved to 
> userland.
>  > 
>  > This will cause issues should cpuctl and the kernel have different code.  
> As a bug in the kernel code may not be present in cpuctl and a cache or tlb 
> maybe detected incorrectly.
>  
>  Please excuse me for being forthright, but I get the sense that this is a
>  sentimental reaction to change. The majority of the information gathered and
>  printed by the kernel was of no use at runtime and was only for eye candy
>  purposes.

Perhaps so, I just prefer to at least have a vague idea if NetBSD gets
the chip or not.

>  Items like the TLB and L1 cache information are never used. The list of
>  feature flags reported was incomplete and even at that, it was already a
>  large amount of information to casually sift through.

So why do we even bother working it out then?  I thought we did use some
of the cache info to determine page colouring.

Perhaps if we just displayed the stuff we do need and use, it would
allow tweaks/updates to be checked, particularly when asked to check
someone elses change works on your hardware.

>  > It also doesn't allow verification of changes to the kernel's detection of 
> the CPU features without adding the printf's back in.
>  
>  Well, I found and fixed quite a few bugs when overhauling it and that was
>  through tedious reading of the code and verification of changes. The
>  printout didn't help me with that.

If the printouts didn't help then should they have been expanded to help?

Thanks,
Chris