Conference orarep::nomahs::sql_services

2207.0. "Dispatcher process uses excessive CPU." by rdb4me.au.oracle.com::DLAWLER (Press any key to continue or any other key to quit...) Thu May 22 1997 04:02

Hi,

A customer has reported problems with SQLSRV dispatcher process using excessive
CPU.
They provided 2 examples of graphs generated by DECps.  Each shows a comparison
between the dispatcher process and the executor process.  Although I can't
include the graphs here, I have provided my observations(*) and included the
customer's narrative(>):
 

System: Rdb7 eco1 on Alpha 2100A 512 mb, SQL/S 7.0

*The First graph shows cpu usage over a 3hr period.
*The executor is peaking at 40% cpu with an average of about 20-25%.
*The dispatcher is peaking at 95% and averaging about 75%.

>The cpu usage of sqlsrv dispatcher is high compared to the executor CPU.
>Note that the executor processes are doing a fair amount of work on the
>database so I would expect them to be much higher in CPU utilization than the
>dispatcher.


*The second graph shows cpu usage over a 48 hr period.
*The executor is present for the first 3 hrs peaking at about 30%, is idle for
*40hrs (approx 0% cpu), then peaks at about 60% for the last 5 hrs.
*The dispatcher peaks at about 60% during the first executor activity, then
*appears to consume 90-95% until the second executor activity, where it appears
*to taper off to 0 over the executor 5 hr period.

>There is a flurry of activity on the executor processes and then the dispatcher
>seems to take a pretty unfair amount of the CPU.


Note: In both cases the dispatcher priority was at 4 whilst the executor
process was at 3.
Setting the priorities to be the same dramatically reduces the CPU usage
of the dispatcher process (even when the CPU is only 60% utilized). 
Is it bad karma to set the priorities of the executor processes 
to below that of the dispatcher and why?


Cheers
Dennis.
Rdb Support,
Asia Pacific GSC,
Oracle WWCS,