CPU, CPU USE, CPU SKEW

Viewpoint

CPU, CPU USE, CPU SKEW

Hi Guys,

I am trying to understand the defintion of CPU, CPU USE, CPU SKEW, IMPACT CPU. I have referred viewpoint manual for this but still not able to grab it. Can anybody explain how these parametrs are calculated. 

CPU USE          9.49% 

CPU               671.6 

CPU SKEW       61.1% 

IMPACT CPU     245.95

I/O                   1,513,061 

I/O SKEW         81.6%

Which DBC table is referred to calculate this?

6 REPLIES
Teradata Employee

Re: CPU, CPU USE, CPU SKEW

Viewpoint gets all of its session data from calling the Monitor Session command in the PM/API.  It doesn't come from a DBC table.  Here are the definitions, mostly lifted from the Viewpoint manual.
  • Request CPU - Number of CPU seconds that have been used by the current request (I'm pretty sure from looking at the numbers your CPU value is Request CPU)
  • Delta CPU - Number of CPU seconds used by the session in the last sampling period
  • CPU Use - Percent of available CPU seconds on the system used during the last sampling period (so CPU Use is Delta CPU / # of available CPU seconds across all nodes on the system during the sample period)
  • CPU Skew - Percentage representing how skewed a query is when comparing the hottest AMP CPU during the last sample period to the average AMP CPU during the last sample period.  61.1% is quite a skewed query.
  • Impact CPU - CPU time in seconds of the highest CPU utilized AMP during the collection interval times the total number of AMPs participating for this session during the last session collection interval
  • I/O - Probably Request I/O, which is the total number of I/Os for the current request
  • I/O Skew - Percentage representing how skewed a query is when comparing the hottest AMP I/O count during the last sample period to the average AMP I/O count during the last sample period.
Hope that helps!

Steve

Re: CPU, CPU USE, CPU SKEW

Steve,

I have a related question to calculate number CPU cycles a particular system can support. For ex: I have a 6700 production box. If i want to calculate the capacity of that box in terms of N number of cycles, how can i do that.

I heard there is a formula to do that. Any comments will be appreciable.

Thanks in advance. 

Teradata Employee

Re: CPU, CPU USE, CPU SKEW

The number of CPU seconds for the entire system, which is used to calculate metrics such as CPU Use as mentioned above, can be calculated quite easily.  Assuming a homogenous system, the formula is:

Number of nodes * Number of CPUs per node * Number of cores per CPU

In the case of coexistent systems Viewpoint accounts for that as it gets the number of CPU cores on each individual node in the system.

Viewpoint always assumes that 100% of the CPU cycles are available when calculating these types of metrics.  In reality, there's some system overhead that will consume a small percentage of the CPU cycles and therefore those won't be available for user work.

Re: CPU, CPU USE, CPU SKEW

Thank you for the quick answer. 

If i wanted to know exactly how many cpu cycles available for 1hr on PROD box with 6650C and 5555H cooexistence system, I think my below formula is correct. Please correct me if i am wrong. I multiplied by 2 for hyperthreading.

NumberOfNode * NumberOfCPUsPerNode*NumberOfCoresPerCPU*2forHyperThreading*3600 sec/hr.

And while counting the nodes, i think i need to consider hot standby nodes too.

Teradata Employee

Re: CPU, CPU USE, CPU SKEW

I don't think you should multiply by 2 for hyperthreading.  Viewpoint doesn't specifically account for hyperthreading.  It relies upon the number of CPUs returned from PM/API, which is also available in the ResUsageSPMA table.

Re: CPU, CPU USE, CPU SKEW

I see, thank you.

I agree for Viewpoint server while calculating the CPU seconds no need to multiply by 2, but what about other systems like 6650, 5550 etc boxes.?