Re: RES: Priority to a mission critical transaction

[Brian Hurt <bhurt(at)janestcapital(dot)com>]

Ron Mayer wrote:

> Before asking them to remove it, are we sure priority inversion
> is really a problem?
>
> I thought this paper: http://www.cs.cmu.edu/~bianca/icde04.pdf
> did a pretty good job at studying priority inversion on RDBMs's
> including PostgreSQL on various workloads (TCP-W and TCP-C) and
> found that the benefits of setting priorities vastly outweighed
> the penalties of priority inversion across all the databases and
> all the workloads they tested.
>
>  
I have the same question.  I've done some embedded real-time 
programming, so my innate reaction to priority inversions is that 
they're evil.  But, especially given priority inheritance, is there any 
situation where priority inversion provides *worse* performance than 
running everything at the same priority?  I can easily come up with 
situations where it devolves to that case- where all processes get 
promoted to the same high priority.  But I can't think of one where 
using priorities makes things worse, and I can think of plenty where it 
makes things better.

Brian