ifx versus POWER7 - SMT4
Hi, We have here IFX 11.50 FC8 running over a new machines, AIX 6.1, Power7 Machine (p740), 16 core option (2 socket, 8 cores each), configured with LPAR. I need some reference, official preferentially about what is better configuration to Informix. Monitoring this machines, I don't see they consumption go over 60% of CPU utilization. (topas, sar, lparstat). At database side, I getting Read queue growing to much at certain moments... I suspect this happen because of the configuration of LPAR. I request to our AIX Admin, 14 CPUs from the physical machine, the configuration made was: ------------------------------ lparstat : Mode : Uncapped Maximum Capacity : 16.00 Entitled Capacity : 14.00 Online Virtual CPUs : 28 Type : Shared-SMT-4 Physical CPU Percentage : 50.00% ------------------------------ With SAR or lpstat I see all CPUs utilized and a little more was configured (because they are uncapped): ------------------------------ System configuration: lcpu=112 ent=14.00 mode=Uncapped 09:30:10 %usr %sys %wio %idle physc %entc runq-sz %runocc swpq-sz %swpocc 09:30:20 59 4 0 37 14.34 102.4 21.1 100 09:30:30 60 3 0 37 14.48 103.4 19.7 90 09:30:40 60 4 0 37 14.34 102.5 20.4 100 09:30:50 60 4 0 37 14.47 103.3 21.6 90 09:31:00 60 3 0 37 14.52 103.7 20.6 100 09:31:10 58 4 0 37 14.41 102.9 21.4 90 09:31:20 60 4 0 36 14.42 103.0 22.1 100 09:31:30 59 4 0 37 14.42 103.0 20.3 90 ------------------------------ Where : lcpu = 28 logical cpu * 4 Threads... Actually the database is configured with 16 CPU VPs . A few days we running it with 28 CPU VPs... and keep the same behave... except the runq-sz naturally grown... but the %usr just keep 60%... My suspect: we are using only 50% of each real physical cpu , because of the "Shared-SMT-4" configuration. I'm have open PMR with AIX support trying understand this... I'm still waiting for answer from them... Any way, for Informix, what is best? Anyone know if I is possible to disable this "Shared-SMX-4" ? If we can, what is better to Informix? Use just a simple and single CPU or keep active this threads?? Configure Informix to 112 CPU VPs ??? I already discuss this here for Sun machines before, where Art explain about the difference of CPU Thread utilization, OS Thread and Informix Thread .... at the end , the best recommendation was disable all Logical/Hardware threads and work with 1 by 1 (cpu vp / physical core cpu). This apply to IBM Power7 processors??? I think... disabling this SMT4 and configuring only 14 logical cpu (lpar) I will have lower overhead over the context switch on AIX Process and keep Ifx CPU VPs running more efficient... Regards Cesar