[asterisk-users] Scaling Asterisk: Dual-Core CPUs not yieldinggains at high call volumes

[Stelios Koroneos]

Hi,

The system seems to be IO bound for some reason.
Reading at the older posts you mentioned that there is no significant disc
activity so it could be ethernet i/o and/or interrupts that are causing this
(old or insuficient ethernet driver maybe ?)
Usually this kind of i/o wait is present on machines that have run out of
memory and need to swap to disk

Also with regard to the higher system usage on multicore systems, its very
probable that its due to task migration from core to core


> Here is something we recently noticed that may explain why the dual-core
> server is under-performing at high call volumes.  The following numbers
> were collected off both servers while they were in production.  Note
> that while they have similar cumulative idle values, the ratio of system
> time to user time on the single-core server is roughly 2.3 to 1, but on
> the dual-core server it is roughly 19.6 to 1.  I'm not quite sure what
> to make of this, but it seems to be very relevant to the problem.
>
>   Mon Apr  2 12:15:01 EDT 2007
>   Idle (sar -P ALL 60 14) (60 seconds 14 slices)
>   Linux 2.6.12-1.1376_FC3smp (4core.imminc.com)         04/02/07
>
>   12:24:01          CPU     %user     %nice   %system   %iowait     %idle
>   12:25:02          all     14.97      0.03     34.25      0.92     49.82
>   12:25:02            0      8.83      0.05     33.60      1.28     56.24
>   12:25:02            1     17.50      0.02     34.60      0.57     47.32
>   12:25:02            2     19.94      0.02     33.52      1.31     45.22
>   12:25:02            3     13.62      0.02     35.29      0.52     50.55
>
>   Thu May 10 15:30:01 EDT 2007
>   Idle (sar -P ALL 60 14) (60 seconds 14 slices)
>   Linux 2.6.12-1.1376_FC3smp (8core.imminc.com)         05/10/07
>
>   15:38:01          CPU     %user     %nice   %system   %iowait     %idle
>   15:39:01          all      2.47      0.01     48.29      0.00     49.23
>   15:39:01            0      2.92      0.00     53.17      0.00     43.91
>   15:39:01            1      2.98      0.00     48.68      0.02     48.33
>   15:39:01            2      2.47      0.02     48.61      0.00     48.91
>   15:39:01            3      2.27      0.00     48.35      0.00     49.38
>   15:39:01            4      2.38      0.02     47.38      0.00     50.22
>   15:39:01            5      2.37      0.02     46.94      0.00     50.67
>   15:39:01            6      2.23      0.02     46.63      0.00     51.12
>   15:39:01            7      2.17      0.02     46.54      0.00     51.27
>
Stelios S. Koroneos

Digital OPSiS - Embedded Intelligence
http://www.digital-opsis.com