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From:Morgan Tocker Date:February 18 2014 3:58pm
Subject:Re: Crash after shutdown/restart
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Hi Jørn,

>> I would say that this sort of performance drop is not typical.  Some
>> users have reported a smaller performance loss in single threaded
>> workloads in 5.6.
> 
> But dropping from an average of 1800 jobs per minute down to 300? I don't 
> think that should be expected.

I would agree with you here.

> A few weeks ago I stopped the test and restored the initial database starting 
> the test over again. Now the performance was back to 1700 jobs per minute, 
> but it slowly went down as the test ran. Yesterday it was down to 300 per 
> minutes and still (but very slowly) dropped.
> 
> Yesterday I did the following:
> 
> * stopped the test
> * dumped all databases
> * stopped the mysql server 5.6
> * Downloaded 5.5.33-log source and installed it
> * Removed all inodb* and ib_log* files
> * Removed all databases
> * Started and initialized mysql
> * Restored all databases
> * Started the test where I left it.
> 
> After a few hours I could see that the performance was back to normal - 1800 - 
> 2000 jobs per minute. There is no sign of drop in performace so far.
> 
> Please explain.

I want to suspect that there might be a specific query regression (where 5.6 has
introduced a new feature, and you fall in an edge case where it is being optimized
incorrectly).

The way to deduce this is to run EXPLAIN for key queries in MySQL 5.6 and 5.5, and compare
for differences:
https://dev.mysql.com/doc/refman/5.6/en/explain.html

When you have one, there are a lot of people on the list that would be happy to pair this
down to a test case, and file a bug.

There is also a switch to disable specific optimizations, so you may have an easy work
around that would allow you to restore back on 5.6:
https://dev.mysql.com/doc/refman/5.6/en/switchable-optimizations.html

- Morgan

Thread
Crash after shutdown/restartJørn Dahl-Stamnes14 Jan 2014
  • Re: Crash after shutdown/restartJesper Wisborg Krogh14 Jan 2014
    • Re: Crash after shutdown/restartJørn Dahl-Stamnes22 Jan 2014
      • Re: Crash after shutdown/restartMorgan Tocker22 Jan 2014
        • Re: Crash after shutdown/restartJørn Dahl-Stamnes18 Feb 2014
          • Re: Crash after shutdown/restartMorgan Tocker18 Feb 2014