On Mon, Jul 15, 2013 at 1:21 PM, Prarit Bhargava <prarit(a)redhat.com> wrote:
I've done some testing across various systems (both
"large" and "small").
Increasing NR_CPUS seems to have a negligible effect. I see about a 1.1M
increase in memory usage when switching between 128 cpus and 5120 cpus. Since
most systems ship with 4G or more these days, I cannot see an issue with
consuming a small amount of memory like this.
1.1M isn't small. We recently declined to build btrfs into the kernel
because it increased the overall memory usage by a similar amount.
Also, we regularly see users and bug reports still in the 2G range.
While it's not an apples to apples comparison, far more Fedora users
are going to be using btrfs than > 128 CPUs. I'm not saying no
immediately, but I'm kinda dubious as to the benefits for Fedora.