Are there any known pitfalls of setting the SPLPAR entitlement well below normal CPU Unit usage levels while using the "Online Virtual" setting to support application peak loads.
My goal is to get more utilization from my FRAME.
I am finding I run out of "CPU Entitlement" before the FRAME is out CPU capacity when looking at my historical utilization levels.
Thanks in advance for your replies.
j.gann 270000SSYT53 Posts
Re: Setting CPU Entitlement Low2012-05-04T05:13:27ZThis is the accepted answer. This is the accepted answer.> RFS wrote:> Are there any known pitfalls of setting the SPLPAR entitlement well below normal CPU Unit usage levels while using the "Online Virtual" setting to support application peak loads.
this is common practice for uncapped lpars. it allows starting a lot of lpars initially while still enabling them to grab additional cycles once the workloads ramp up.
the pitfall is that small entitlements will cause more frequent rescheduling by the hypervisor (under competition, lpars are forced off after they have used up their entitlement although they might be reconsidered for running again later on). the negative side effect is that very probably the memory caches are invalidated during this reschedule (different lpar, different code and data).
I'd use a strategy to give the "performance-wise important" lpars enough entitlement for their typical workload and the "not-so important" ones a minimum.
for details check out nigel griffith's excellent article series about power(7) affinity on dw called "local, near & far" here on dw.