The real time scheduler is really for applications that need to respond in
"hard" time, for example control of industrial machinery. Hard scheduling
wouldn't necessarily result in higher throughput, it would only result in
predictable response times. You may be able to get very fast responses, but
you are trading this off against lowered concurrency, as the only way to
guarantee a response within a given time is to ensure that you have the
resources available to do so.
Similarly, changing the priority of processes doesn't buy you very much, as
you will be creating a bottleneck at the lowest-priority process. And "nice"
is only a hint to the scheduler; it is by no means mandatory. Solaris
doesn't really support what you want to do, which is to define minimal
levels of system resource availability on a per-process basis (you can do
this on OS/390 and VMS).
If you are running on high end Sun kit, you can logically partition the
system, for example you could reserve a group of CPUs for an instance of
Solaris that ran Oracle exclusively, segregating it from the other
applications running on the machine. In effect, you are making one physical
server behave as multiple logical servers, each one running its own Solaris
and behaving essentially as a separate machine. The benefit of this approach
over and above just moving Oracle to a separate machine is that you can
shuffle CPUs around between partitions, for example during periods of peak
load, add more CPUs to Oracle, but perhaps overnight move those CPUs to
another task (perhaps running batch jobs in a separate instance, or even
non-Oracle, compute intensive jobs). Doing this would mean that you had to
retune PQO (and possibly other variables also if it corresponds to large
load spikes, and you can take the time for a restart) every time you added
or remove resources from the partition. For example, if you added more
memory to your partition you might want to alter the SGA.
It will be a mild performance hit, but if you want to know what is really
using system resources in your system, try running with process accounting
enabled for a while.
Cheers,
g.
-----Original Message-----
Sent: 13 June 2001 16:21
To: Multiple recipients of list ORACLE-L
Two comments:
1) Why not just re-NICE the shadow (or offending procs)
2) Last I heard oracle does not recommend running
their procs at differing NICE levels.
-----Original Message-----
Sent: Tuesday, June 12, 2001 6:33 PM
To: Multiple recipients of list ORACLE-L
Folks,
Does anyone know how to exploit the real-time scheduler in Solaris? I can
only find vague references to this on the web.
We're considering using the real-time scheduler for Oracle background
processes on our busiest Solaris boxes (that support 2-3k connections). We
want to make Unix bias the Oracle background processes for CPU, all other
things being equal. We had some consultants suggesting our MTS config
wasn't getting the cycles it needed after we called into question their SQL
(which is too long a story for me to get into -- I'll begin ranting about
big consulting companies. :)
Thanks,
Steve
Steve Austin
DBA for Unix-based systems
Enterprise Data Center Operations, XO Communications
email: [EMAIL PROTECTED]
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