Bug 218814

Summary: Changing the default time source from PMtimer to TSC
Product: Red Hat Enterprise Linux 5 Reporter: Bhavna Sarathy <bnagendr>
Component: kernelAssignee: Peter Martuccelli <peterm>
Status: CLOSED WONTFIX QA Contact: Brian Brock <bbrock>
Severity: medium Docs Contact:
Priority: high    
Version: 5.0CC: bnagendr, jfeeney, peterm, prarit
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2013-11-04 02:07:48 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Description Bhavna Sarathy 2006-12-07 17:33:15 UTC
Description of problem:
The default PMtimer is not scalable and performance numbers with Oracle timed 
& non-timed stats do not give the customer a good out of the box experience.
With GH TSC will be the default timer and the code is in RHEL5, so the 
change/discussion is for the Opterons with the TSCnow patch.

(The modified kernel in reference here is cpuid(0) instruction added to the 
RDTSCP code path to simulate the GH latencies).

With modified kernel to simulate GH latencies:

                        HPET         TSC            TSC vs HPET

w/ No timed Stats      36251.6       41675.40       1.15

W/ timed Stats         34419.2       40342.80        1.17

%diff                     5.3%              3.3%


w/ no timed stats:  TSC is 15% faster than HPET

w/ timed stats: TSC is 17% faster than HPET

Beta2 kernel:

Oracle 10G         HPET     PMtimer      TSC    TSC vs PMtimer    TSC vs HPET

w/ notimed stat     37454     39495     43947        1.11             1.17

timed stats         32968     33995     42096        1.24             1.27

 % diff              13.6%    16.18%    4.4%  


w/ notimed Stats  - 11% faster than pmtimer, and 17% faster than HPET 

w/ timed Stats on - 24% faster than pmtimer, and 27% faster than HPET

Comment 1 Adam Jackson 2006-12-15 20:29:04 UTC
*** Bug 218810 has been marked as a duplicate of this bug. ***

Comment 2 Adam Jackson 2006-12-15 20:29:05 UTC
*** Bug 218812 has been marked as a duplicate of this bug. ***

Comment 3 Adam Jackson 2006-12-15 20:29:25 UTC
*** Bug 218813 has been marked as a duplicate of this bug. ***

Comment 5 RHEL Product and Program Management 2012-10-30 06:02:41 UTC
This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.

Comment 6 John Feeney 2013-11-04 02:07:48 UTC
This Bugzilla has been reviewed by Red Hat and is not planned on being
addressed in Red Hat Enterprise Linux 5, and therefore is being closed.
If this bug is critical to production systems, please contact your Red
Hat support representative and provide a sufficient business justification
in order to re-open it.