[lkml]   [2008]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [BUG] x86 kenel won't boot under Virtual PC

On Mon, 8 Sep 2008, Andi Kleen wrote:
> Originally it was an option because the 128 byte cache line it selects
> caused bloat in several important data structures. That was back
> then when cache line padded NR_CPUs arrays were still pretty common.
> I don't know if it's still a problem, but before making it default y
> it would be good to check the dynamic+static memory cost at least.

Btw, I do think that the whole NOPL issue is separate from all the other
issues. There can be _other_ cases where it really is worth doing some
"generic" optimizations or being more "specific", and my argument really
is that NOPL is _not_ one of those cases.

So I'm still not sure that X86_GENERIC is necessarily the answer. The
answer may be:

- never use NOPL statically unless we _know_ it works (eg x86-64)

- never allow such a stupid decision by gcc as to use NOPL on x86-32.

..and then leave X86_GENERIC alone wrt everything else.

Peter - does gcc actually use NOPL in _32-bit_ code too? It really seems
to be a stupid decision to make a binary not run on other CPU's over
something as trivial as that. That's something I'd expect out of an Intel
compiler just to mess with AMD, not out of gcc.


 \ /
  Last update: 2008-09-08 19:07    [W:0.114 / U:2.168 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site