How Resources are Shared in the SLES 11 Priority Scheduler - comment by carrie

Sachin,
 
Are you saying that all 4 workloads on SLG Tier 1 in combination have a global weight of 85%?  And that Timeshare workloads will share a global weight of 15%?
 
And can I assume that all the batch work (which is high priority at this time) is running in SLG Tier 1?
 
Assuming that is the case, then CPU will be allocated (offered) to the SLG Tier workloads based on each workoad's individual allocation percent.  CPU allocations align strictly with the setup that has been defined.
 
But being offered CPU and having that CPU be consumed are two different things.    Contention for other resources could hold back SLG Tier workloads from consuming all the CPU they are offered.   And while I/O is prioritized, if any of the work running in a workload is I/O-intensive, it's CPU usage patterns  will not align as closely to what it's allocation percent entitles it to.   That is because I/O is issued with system throughput as a priority, so things like merging I/O requests (that are close to each other on disk) that come from high and low priority workloads takes place, diluting priority differentiation.   In addition, if there are different speeds of disk in the system, SSD on hot storage will get serviced faster than one on cold storage.  And in order to exhibit any I/O priority difference, I/O requests must be targeting the same disk, otherwise I/Os can be issued simultaneously.   
 
See Section 5.4 in the I/O chapter of the priority scheduler orange book for more detail on how I/O contention may make a workload look like it is not adhering to the prioritization scheme.
 
I would guess most of the batch work is I/O-intensive.  If so, that will make consumption of CPU as a measure of priority effectiveness less useful.  
 
With more concurrency in Timeshare, there could be greater contention for I/O, and that could be a factor.   If skew is very great, that can also make clear prioritization a little more uneven.   If one AMP is congested, and others are not, then those other AMPs will slow down in their CPU consumption, and priority differentation will be more difficult to detect.    
 
Thanks, -Carrie