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Bug 1487729

Summary: Improve performance of linearstore when the flush timeout is set to a low value
Product: Red Hat Enterprise MRG Reporter: Mike Cressman <mcressma>
Component: qpid-cppAssignee: messaging-bugs <messaging-bugs>
Status: CLOSED ERRATA QA Contact: Petr Matousek <pematous>
Severity: high Docs Contact:
Priority: high    
Version: 3.2CC: jross, pematous, zkraus
Target Milestone: 3.2.6   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: qpid-cpp-1.36.0-11 Doc Type: Bug Fix
Doc Text:
Cause: If the broker journal-flush-timeout config option is set to something below 1ms, Consequence: the broker continuously uses a noticeable amount of CPU, even at idle. Fix: The flush code was reworked to minimize CPU usage if there are no messages pending. Result: Now there almost no CPU usage when the broker is idle, even if the journal-flush-timeout option is set to a very low value.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2017-10-16 14:29:04 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1494952    
Bug Blocks:    

Description Mike Cressman 2017-09-01 18:30:57 UTC 
Description of problem:
If the broker journal-flush-timeout is set to something below 1ms,
the broker continuously uses a noticeable amount of CPU, even at idle. 


Version-Release number of selected component (if applicable):
qpid-cpp-1.36.0-6


How reproducible:
Always, but it's more visible if you set the timeout to 100ns or even 10ns.


Steps to Reproduce:
1. set journal-flush-timeout to 100ns
2. start the broker (qpidd)
3. check the CPU usage of qpidd

Actual results:
The broker uses a noticeable amount of CPU at idle.


Expected results:
The broker uses almost no CPU at idle.


Additional info:
Without the fix, the linearstore flush timers run continuously and the CPU use is visible.  The fix keeps the timers from running unless there is data to process.  When the broker is busy, things should be similar to what they were before, or maybe slightly better.
Comment 2 Petr Matousek 2017-09-19 13:16:37 UTC 
This issue has been fixed. Verified on all supported platforms.

-> VERIFIED
Comment 4 Petr Matousek 2017-10-03 15:27:54 UTC 
The issue has been fixed. Verified with all available reproducers for Bug 1494846  and Bug 1494952 on all supported platforms. Internal test case has been linked.

-> VERIFIED
Comment 5 Petr Matousek 2017-10-03 15:29:29 UTC 
verified with:
* qpid-cpp-1.36.0-11
Comment 7 errata-xmlrpc 2017-10-16 14:29:04 UTC 
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.

https://access.redhat.com/errata/RHBA-2017:2892