Bug 966775 - [RHEL 6.4] BUG glibc causing double-whetstone performance degradation when compared to RHEL 6.3.
[RHEL 6.4] BUG glibc causing double-whetstone performance degradation when co...
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: glibc (Show other bugs)
x86_64 Linux
medium Severity high
: rc
: ---
Assigned To: Siddhesh Poyarekar
Arjun Shankar
: Patch
Depends On:
  Show dependency treegraph
Reported: 2013-05-23 18:55 EDT by Kevin Toyama
Modified: 2016-11-24 07:15 EST (History)
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:
Last Closed: 2013-11-21 06:02:17 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
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

  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):

How reproducible:

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.


Note You need to log in before you can comment on or make changes to this bug.