Bug 966775 – [RHEL 6.4] BUG glibc causing double-whetstone performance degradation when compared to RHEL 6.3.

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Bug 966775 - [RHEL 6.4] BUG glibc causing double-whetstone performance degradation when compared to RHEL 6.3.

Summary:	[RHEL 6.4] BUG glibc causing double-whetstone performance degradation when co...

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	glibc (Show other bugs)
Sub Component:
Version:	6.4
Hardware:	x86_64 Linux

Priority	medium Severity high
Target Milestone:	rc
Target Release:	---
Assigned To:	Siddhesh Poyarekar
QA Contact:	Arjun Shankar
Docs Contact:

URL:
Whiteboard:
Keywords:	Patch

Depends On:
Blocks:
	Show dependency tree / graph

Reported:	2013-05-23 18:55 EDT by Kevin Toyama
Modified:	2016-11-24 07:15 EST (History)
CC List:	10 users (show)

See Also:
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:	The improvements RHBA-2013:0279 made to the accuracy of floating point functions in the math library caused performance regressions for those functions. The performance regressions were analyzed and a fix was applied that retains the current accuracy but reduces the performance penalty to acceptable levels.
Story Points:	---
Clone Of:
Environment:
Last Closed:	2013-11-21 06:02:17 EST
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Candidate fix (6.01 KB, patch) 2013-06-07 10:16 EDT, Siddhesh Poyarekar	no flags	Details \| Diff
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2013:1605	normal	SHIPPED_LIVE	Moderate: glibc security, bug fix, and enhancement update	2013-11-20 16:54:09 EST

Groups: None (edit)

Description Kevin Toyama 2013-05-23 18:55:10 EDT

Description of problem:
When running UnixBench5.1.3 tests on a RHEL6.4 system with the latest glibc version there is a noticeable performance loss in the double-whetstone test (around 50% difference).  When using the patched glibc from BZ964044, http://people.redhat.com/yoguma/.bz892635 there is still about a 20% loss in performance.

Version-Release number of selected component (if applicable):
glibc-2.12-1.107.el6.x86_64
glibc-2.12-1.107.el6.1.bz892635.x86_64

How reproducible:
always.

Steps to Reproduce:
- Build a RHEL6.3 x86_64 system, mine is built with 4 CPU, 4GB memory.
- Download, compile UnixBench5.1.3.tgz from http://code.google.com/p/byte-unixbench/downloads/list
- The one benchmark number they are checking on is the double-whetstone run, the others are within a <10% gap which they seem to be satisfied with.
# ./Run -c 1 -i 20 whets
- gather the Results
- Build a RHEL6.4.z system with latest packages and run UnixBench, gather results
- Install the patch glibc packages from here: http://people.redhat.com/yoguma/.bz892635/ and rebuild, re-run UnixBench. gather results.

Actual results: RHEL6.4.z glibc run is 40% slower than 6.3, and 6.4 + patch glibc is still 20% slower than 6.3.


Expected results: 
Same or better performance.


Additional info:

Comment 3 Siddhesh Poyarekar 2013-05-24 03:03:14 EDT

I'll take this.

Comment 10 Siddhesh Poyarekar 2013-06-07 10:16:01 EDT

Created attachment 758173 [details]
Candidate fix

Comment 38 errata-xmlrpc 2013-11-21 06:02:17 EST

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2013-1605.html

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