[NTLUG:Discuss] Disk I/O timings.

[Steve Baker]

Dan Carlson wrote:
> 
> Are you using static realtime priorities for your high priority
> processes? 

Yes.

> If not, this might help make the behavior of the standard
> kernel be more predictable for your application.  I wasn't aware until
> recently that standard linux supports two types of process priorities,
> dynamic and static.  The dynamic priority is the one everyone is
> familiar with, viewing with ps or top, controlling with nice, etc.
> The static realtime priority is used for processes that must take
> precedence over all dynamic priority processes.

Yes - but you have to be quite careful - if you crank your process priority
statically higher than things like X-windows, you can lock your system up
fairly impressively!

Fortunately, you have to be root to do any serious harm.

> On SuSE 7.2 there are
> getpriority and setpriority commands that let you view and modify the
> static realtime priority of a process.  You can also specify the
> realtime scheduling policy you want the process to use, round-robin or
> fifo.
> 
> I found this to be a good reference on kernel scheduling:
> 
> http://www.oreilly.com/catalog/linuxkernel/chapter/ch10.html

Thanks - I'll check it out. 

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