Details
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Type:
Bug
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Status: Closed
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Priority:
Major
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Resolution: Won't Fix
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Affects Version/s: None
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Fix Version/s: 2.7.0
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Component/s: SyncGateway
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Security Level: Public
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Labels:None
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Sprint:CBG Sprint 26
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Story Points:5
Description
During perf testing on a 48 core machine, one perf stat measuring the CPU usage via top was showing ~4000% (i.e. all cores running at ~85%)
However, the process_cpu_percent_utilization stat, was only ever showing about 800%
After looking at the code that calculates this stat a little (calculateProcessCpuPercentage), it's non-trivial, so we need to verify it's doing the right thing, and determine the reason for the huge difference above.
Following discussion we will leave the stat as is. It appears that it is missing a number of components which are used in top to calculate the CPU usage. The calculation used by a proposed library is as follows:
c.User + c.System + c.Nice + c.Iowait + c.Irq + c.Softirq + c.Steal + c.Guest + c.GuestNice + c.Idle + c.Stolen, however, we appear to be only counting the user and system stat.
A fix to include these other components is on branch CBG-439-3, however, as it uses a different library and also a new dependency (for windows support) we are not putting this change in for now.
A DOC ticket to make customers aware that this calculation only takes into account user and system time is tracked as
DOC-5499