Re: RFC: revert request for cpuidle patches e11538d1 and 69a37bea

From: Rik van Riel
Date: Fri Jul 26 2013 - 14:13:24 EST

On 07/26/2013 01:33 PM, Jeremy Eder wrote:

We believe we've identified a particular commit to the cpuidle code that
seems to be impacting performance of variety of workloads. The simplest way to
reproduce is using netperf TCP_RR test, so we're using that, on a pair of
Sandy Bridge based servers. We also have data from a large database setup
where performance is also measurably/positively impacted, though that test
data isn't easily share-able.

Included below are test results from 3 test kernels:

kernel reverts
1) vanilla upstream (no reverts)

2) perfteam2 reverts e11538d1f03914eb92af5a1a378375c05ae8520c

3) test reverts 69a37beabf1f0a6705c08e879bdd5d82ff6486c4

In summary, netperf TCP_RR numbers improve by approximately 4% after
reverting 69a37beabf1f0a6705c08e879bdd5d82ff6486c4. When
69a37beabf1f0a6705c08e879bdd5d82ff6486c4 is included, C0 residency never
seems to get above 40%. Taking that patch out gets C0 near 100% quite
often, and performance increases.

Could you try running the tests with just the repeat mode
stuff from commit 69a37bea excluded, but leaving the common
infrastructure and commit e11538?

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