Gert Wagger wrote:
Does anyone know what 'ProcessPriorityLevel' does within the firebird configuration file?
I understand you can set its value to a positive number.
But no guidance is given to what the number should be.
Should I put 1000000 or 5 or 54 ?
No guidance is given to what the effect of providing a positive number will do and how high that number should be.
Helen Borrie answers:
It applies only to Windows and it's a can of worms. See http://msdn2.microsoft.com/en-us/library/ms685100.aspx
It's a base setting only: the priority at which the process starts. Processes change priority constantly as they move up and down the scheduling queue. A process will get a slice of CPU if there are no higher priority processes waiting in the queue at the time the slice becomes available.
If trying it out, bear in mind that Firebird's default setting of zero is equivalent to "Normal", which is 8 in Windows terms. The Windows scale on 32-bit systems ranges from RealTime (24) down to 4 (Low) for Priority Level and 31 down to ?? for priority class. AFAIU, the scale that Firebird uses is based on a combination of both the class and the level.
Should I put 1000000 or 5 or 54 ?
One thing you could do is draw a graph of the three scales to work out the correspondences; then (in the lab) play about with setting the priorities during run-time using Task Manager. From what I can tell, boosting the priority to more than 5 (13 in Windows terms) is likely to bring your system to a standstill.
No guidance is given to what the effect of providing a positive number will do and how high that number should be.
That's true. It's not very encouraging, which is what makes it as useful as it could be. By this I mean it is totally specific to the Windows environment you are running. There are no "recommended numbers".
I believe it was implemented back in 16-bit Windows time, when it was (comparatively) easier to know the relative priorities of running processes and recognise the effects of altering the base priority. That said, I've never heard of anyone who succeeded in influencing how a 32-bit Windows apportions CPU time in any way that dramatically affected performance...if you manage to do it, a report on your tests would be most welcome.