CPU Ready Time – Blog Part II

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Jim Hannan (@HoBHannan), Principal Architect

This is the follow up blog to CPU Ready Part I. I have been using the following tables for around six months now. I find them very helpful in quickly determining if a virtual machine is having issues with CPU Ready Time.

What is CPU Ready Time?

CPU Ready Time is measured as a summation value in vSphere, different chart time spans will effect the redline value. Here’s a break down of the summations for each time period:

  • Real-time: 20 seconds
  • Past Day: 5 minutes (300 seconds)
  • Past Week: 30 minutes (1800 seconds)
  • Past Month: 2 hours (7200 seconds)
  • Past Year: 1 day (86400 seconds)

This can be time consuming to collect during troubleshooting, so we supplied the redline for each time period in Tables 1-5.

The formula: CPU Ready % = (Summation value / (chart update interval in seconds x 1000)) x 100

Reference: Update intervals (KB article 2002181): http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2002181

Table 1 – CPU Ready Time (Real Time)

For CPU Ready Time measured by Real Time the interval is every 20 seconds.

ms (milliseconds) % (percent)
1000 5.0
900 4.5
800 4.0
700 3.5
600 3.0
500 2.5
400 2.0
300 1.5
200 1.0
100 0.5
50 0.25

 

Table 2 – CPU Ready Time (Day)

For CPU Ready Time measured by Day the interval is every 300 seconds.

ms (milliseconds) % (percent)
15000 5.0
13500 4.5
12000 4.0
10500 3.5
9000 3.0
7500 2.5
6000 2.0
4500 1.5
3000 1.0
1500 0.5
750 0.25

 

Table 3 – CPU Ready Time (Week)

For CPU Ready Time measured by Week the interval is every 30 minutes.

ms (milliseconds) % (percent)
90000 5.0
81000 4.5
72000 4.0
63000 3.5
54000 3.0
45000 2.5
36000 2.0
27000 1.5
18000 1.0
9000 0.5
4500 0.25

 

Table 4 – CPU Ready Time (Month)

For CPU Ready Time measured by Month the interval is every 2 hours.

ms (milliseconds) % (percent)
360000 5.0
324000 4.5
288000 4.0
252000 3.5
216000 3.0
180000 2.5
144000 2.0
108000 1.5
72000 1.0
36000 0.5
18100 0.25

 

Table 5 – CPU Ready Time (Year)

For CPU Ready Time measured by Year the interval is every 864000 seconds.

ms (milliseconds) % (percent)
4320000 5.0
3888000 4.5
3456000 4.0
3024000 3.5
2592000 3.0
2160000 2.5
1728000 2.0
1296000 1.5
864000 1.0
432000 0.5
216000 0.25

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