Re: page table lock patch V15 [0/7]: overview

Christoph Lameter
2005-01-12T17:37:27Z

On Wed, 12 Jan 2005, Christoph Hellwig wrote:

> On Wed, Jan 12, 2005 at 08:39:21AM -0800, Christoph Lameter wrote:
> > The future is in higher and higher SMP counts since the chase for the
> > higher clock frequency has ended. We will increasingly see multi-core
> > cpus etc. Machines with higher CPU counts are becoming common in business.
>
> An they still are absolutely in the minority. In fact with multicore
> cpus it becomes more and more important to be fast for SMP systtems with
> a _small_ number of CPUs, while really larget CPUs will remain a small
> nische for the forseeable future.

The benefits start to be significant pretty fast with even a few cpus
on modern architectures:

Altix no patch:
Gb Rep Threads User System Wall flt/cpu/s fault/wsec
1 10 1 0.107s 6.444s 6.055s100028.084 100006.622
1 10 2 0.121s 9.048s 4.082s 71468.414 135904.412
1 10 4 0.129s 10.185s 3.011s 63531.985 210146.600

w/patch
Gb Rep Threads User System Wall flt/cpu/s fault/wsec
1 10 1 0.094s 6.116s 6.021s105517.039 105517.574
1 10 2 0.134s 6.998s 3.087s 91879.573 169079.712
1 10 4 0.095s 7.658s 2.043s 84519.939 268955.165

There is even a small benefit to the single thread case.

Its not the case that this patch only benefits systems with a large number
of CPUs. Of course that is when the benefits results in performance gains
by orders of magnitude.