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

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

The following reply was made to PR port-i386/38634; it has been noted by GNATS.

From: Chris Gilbert <chris%dokein.co.uk@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: port-i386-maintainer%netbsd.org@localhost, 
gnats-admin%netbsd.org@localhost, 
 netbsd-bugs%netbsd.org@localhost, chris%NetBSD.org@localhost
Subject: Re: port-i386/38634: x86 kernels no longer produces information about
 cpus
Date: Mon, 12 May 2008 19:47:34 +0100

 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