Heavy I/O blocks FreeBSD box for several seconds

[Ivan Voras]

On 07/07/2011 22:08, Steve Kargl wrote:

> 4BSD kernel gives for N = Ncpu + 1.
>
> 34 processes:  6 running, 28 sleeping
>
>    PID USERNAME  THR PRI NICE   SIZE    RES STATE   C   TIME    CPU COMMAND
>   1417 kargl       1  71    0   370M   294M RUN     0   1:30 79.39% sasmp
>   1416 kargl       1  71    0   370M   294M RUN     0   1:30 79.20% sasmp
>   1418 kargl       1  71    0   370M   294M CPU2    0   1:29 78.81% sasmp
>   1420 kargl       1  71    0   370M   294M CPU1    2   1:30 78.27% sasmp
>   1419 kargl       1  70    0   370M   294M CPU3    0   1:30 77.59% sasmp

> ULE kernel gives for N = Ncpu + 1.
>
> 34 processes:  6 running, 28 sleeping
>
>    PID USERNAME  THR PRI NICE   SIZE    RES STATE   C   TIME    CPU COMMAND
>   1318 kargl       1 103    0   370M   294M CPU0    0   1:31 100.00% sasmp
>   1319 kargl       1 103    0   370M   294M RUN     1   1:29 100.00% sasmp
>   1322 kargl       1  99    0   370M   294M CPU2    2   1:03 87.26% sasmp
>   1320 kargl       1  91    0   370M   294M RUN     3   1:07 60.79% sasmp
>   1321 kargl       1  89    0   370M   294M CPU3    3   1:06 55.18% sasmp

I can confirm this. Look at the priorities column for the two cases. For 
some reason (CPU affinity?) the loads get asymmetrical on ULE.