Bug 163397 - cpuspeed doesn't handle hyperthreaded cpu's effectively
cpuspeed doesn't handle hyperthreaded cpu's effectively
Status: CLOSED INSUFFICIENT_DATA
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: kernel-utils (Show other bugs)
4.0
All Linux
medium Severity medium
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Assigned To: Jarod Wilson
Brian Brock
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Depends On:
Blocks:
  Show dependency treegraph
 
Reported: 2005-07-15 16:17 EDT by Eric Jones
Modified: 2007-11-30 17:07 EST (History)
2 users (show)

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Doc Type: Bug Fix
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Last Closed: 2007-06-04 17:37:19 EDT
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Description Eric Jones 2005-07-15 16:17:53 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050512 Red Hat/1.0.4-1.4.1 Firefox/1.0.4

Description of problem:
When using a HyperThreaded Pentium 4 CPU, the cpuspeed daemon doens't use an effective algorithm for determining the current CPU utilizization.  Since a single CPU intensive process only runs on one "virtual" CPU, the other CPU appears 100% idle, giving a net system usage of 50%.  cpuspeed sees this and lowers the clock speed, slowing down the otherwise CPU intensive application.  When running on a hyperthreaded system, cpuspeed should use the most active "virtual" processor as its gauge for current system activity.

Version-Release number of selected component (if applicable):
kernel-utils-2.4-13.1.48

How reproducible:
Always

Steps to Reproduce:
1. start cpuspeed
2. run an intense cpu benchmark on one "virtual" processor
3. cat /proc/cpuinfo and watch the processor get slowed to its lowest state (2.8 GHz on my 3.6 GHz box)
  

Actual Results:  The cpu was frequency scaled down to its lowest state.

Expected Results:  The cpu should have run at the maximum clock speed since the benchmark was utilizing 100% of one of the "virtual" processors.

Additional info:
Comment 1 Jarod Wilson 2007-01-24 09:53:32 EST
Is this still an issue with the latest RHEL4 kernel and kernel-utils packages?
I'm taking over all cpu frequency scaling bugs, and trying to work my way
through them...
Comment 2 Jarod Wilson 2007-06-04 17:37:19 EDT
4+ months of no activity, 1.5+ years since hearing from the original poster,
closing out bug.

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