lkml.org 
[lkml]   [2000]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: Cache coherency... and locking
Date
In article <Pine.LNX.4.10.10007272155260.20583-100000@waste.org>,
Oliver Xymoron <oxymoron@waste.org> wrote:
>On Thu, 27 Jul 2000, Linda Walsh wrote:
>
>> Some followup -- it was setting/testing 1 integer. So it
>> seems it can safely be done w/o lock.
>
>Cool.
>
>> Talking with an internal engineer here -- NUMA uses MESI
>> cache control similarly to the i386 cache coherency model,
>> so a write of one CPU to a an area of memory will be seen
>> on other processors as soon as they ask for that memory.
>
>That's specific to MIPS. A general Linux NUMA model probably won't assume
>coherence.

I disagree.

If it's not ccNUMA, then the different nodes should run _different_
copies of the OS, and you'd basically have a multi-OS system rather than
single image. Non-cache-coherent hardware simply is not worth handling
as a single image, I suspect.

So at least right now my personal plan would be to consider non-cc NUMA
to be just a cluster. Multiple machines backed with a fast
interconnect, and communication between them happens as if they were
separate machines (and the fast interconnect is then used as a way to
make those separate machines able to communicate with each other really
well).

Most current/modern NUMA designs are ccNUMA anyway, as far as I can
tell. I don't know of anybody who seriously makes a non-cc machine any
more. People know how to make efficient cache controllers, and it just
makes the machines _soo_ much more usable that anybody who isn't cache
coherent really deserves to be ridiculed.

Linus

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:57    [W:0.267 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site