Re: Thread Thrashing under Win32

On Jun 8, 11:28 am, BD <robert.d..._at_gmail.com> wrote:
> I'm working with a developer to deploy Oracle db 10.2.0.3 64-bit under
> Win64. Custom front-end app.
>
> He's asking a question which seems relevant to Oracle architecture,
> but I find no mention of this term anywhere on Metalink.
>
> Basically, he's concerned that the processes parameter in the db
> (which has been set moderately high for initial testing) will result
> in the same number of threads being created in the Oracle Windows
> process - and that this high number of threads will result in 'thread
> thrashing' (a term I wasn't familiar with until today), which will
> limit scalability.
>
> I gather that 'thread thrashing' is a situation where a process slows
> down because of excessive context switching between the threads inside
> the process.
>
> My response is pretty pragmatic - let's not worry about that problem
> unless we have specific reason to worry about it, or unless we see
> evidence of a problem in the Dev environment.
>
> Meanwhile, I'm trying to identify a precedent wherein someone has
> actually *seen* performance issues related to context switching of
> this kind in a Win32/Win64 deployment.
>
> Thus far I'm coming up dry.
>
> Does anyone know of any 'guidelines' Oracle provides which would limit
> the number of processes (and therefore threads in the OS process)
> because of a concern like this? I've tried looking for 'thread
> thrashing' on Metalink, and predictably get nothing at all - 'Context
> Switching' isn't leading me to anything of use either.
>
> I'd like to tell this gent that thread thrashing of this kind is not a
> concern - but I'd prefer to have some kind of architectural provision
> in front of me, to back that up... plus, assuming this kind of
> excessive context switching within the Win32 process is even a
> possibility, I'm not clear how you'd identify that it's occurring...
>
> Thanks for any suggestions...

"With a thread, multiple entities can use the same process, thus avoiding context switches."
http://ewhalen.blogspot.com/2006_05_01_ewhalen_archive.html

White paper that notes threads switch context faster than processes and share more data structures:
http://www.oracle.com/technology/tech/windows/rdbms/Oracle_10gR2_Windows_DB_Architecture_TWP.pdf

My speculation is some java or mysql or perl thread-thrashing has morphed into a windows myth. I'm anti-windows, but even more antimyth.

jg

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