Re: Scaling noise

Nick Piggin
2003-09-04T03:20:52Z

Steven Cole wrote:

>On Wed, 2003-09-03 at 20:35, William Lee Irwin III wrote:
>
>>On Wed, Sep 03, 2003 at 08:19:26PM -0600, Steven Cole wrote:
>>
>>>I would never call the SMP locking pathetic, but it could be improved.
>>>Looking at Figure 6 (Star-CD, 1-64 processors on Altix) and Figure 7
>>>(Gaussian 1-32 processors on Altix) on page 13 of "Linux Scalability for
>>>Large NUMA Systems", available for download here:
>>>http://archive.linuxsymposium.org/ols2003/Proceedings/
>>>it appears that for those applications, the curves begin to flatten
>>>rather alarmingly. This may have little to do with locking overhead.
>>>
>>Those numbers are 2.4.x
>>
>
>Yes, I saw that. It would be interesting to see results for recent
>2.6.0-textX kernels. Judging from other recent numbers out of osdl, the
>results for 2.6 should be quite a bit better. But won't the curves
>still begin to flatten, but at a higher CPU count? Or has the miracle
>goodness of RCU pushed those limits to insanely high numbers?
>

They fixed some big 2.4 scalability problems, so it wouldn't be as
impressive as plain 2.4 -> 2.6. However there are obviously hardware
scalability limits as well as software ones. So a more interesting
comparison would of course be 2.6 vs LM's SSI clusters.