On 05/20/2012 11:23 AM, Ruben Kerkhof wrote:
On Sun, May 20, 2012 at 2:32 PM, Gilboa Davara
> On Sun, May 20, 2012 at 4:07 AM, Josh Boyer <jwboyer(a)redhat.com> wrote:
>> On Sat, May 19, 2012 at 02:54:33PM +0200, Xose Vazquez Perez wrote:
>>>> * Tue Jan 17 2012 Dave Jones <davej(a)redhat.com>
>>>> - Rawhide builds now use MAXSMP on x86.
>>>> - For release builds, set x86-64 to support 64 CPUs.
>>>> If larger systems become widespread, we can increase in an update.
>>> amd: 4sockets * 16cores = 64
>> Awesome. Got that covered still.
>>> intel: 4sockets * 10cores * 2threads = 80
>> Which particular CPU/Motherboard combo is that, and how often do we see
>> it in Fedora?
>> I'm not opposed to bumping it up to 128 or something, but I'm curious
>> how many people are actually going to see benefits.
> At least in my case I did run Fedora 12-16 on 4S and 8S machines to
> test software scalability on (extreme) high-end hardware.
> Though, IMHO anyone that's crazy enough to run Fedora on a high-end
> 4S/8S machine is more than capable of rebuilding the kernel with
> CONFIG_NR_CPUS 256...
> However, given the fact that x86_64 machines tend to be far less
> memory constrained than i686 machines, I doubt that raising the limit
> to 128 will cause too many issues. (Isn't NR_CPUS == 512 in el6?)
It's even higher these days:
grep NR_CPUS /boot/config-2.6.32-220.13.1.el6.x86_64
This is from RHEL which has a markedly different user base than Fedora does. I
remember setting this in RHEL based on a partner request who ships LARGE systems
(4096 CPUs, many many many TB of memory).
This is not the number you want for Fedora.
I'm curious, has anyone measured what the memory overhead is of
keeping NR_CPUS at 512?
I think we did that in RHEL. It is insignificant IIRC. I'll try and dig out