Re: sysbench throughput degradation in 4.13+

[Eric Farman <farman@linux.vnet.ibm.com>]

On 09/22/2017 11:53 AM, Peter Zijlstra wrote:
> On Fri, Sep 22, 2017 at 11:03:39AM -0400, Eric Farman wrote:
>> Hi Peter, Rik,
>>
>> With OSS last week, I'm sure this got lost in the deluge, so here's a
>> friendly ping.
> 
> Very much so, inbox is a giant trainwreck ;-)

My apologies.  :)

> 
>> I picked up 4.14.0-rc1 earlier this week, and still see the
>> degradation described above.  Not really a surprise, since I don't see any
>> other commits in this area beyond the ones I mentioned in my original note.
>>
>> Anyway, I'm unsure what else to try or what doc to pull to help debug this,
>> and would appreciate your expertise here.  We can repro this pretty easily
>> as necessary to help get to the bottom of this.
>>
>> Many thanks in advance,
> 
> Could you describe your sysbench setup? Are you running it on mysql or
> postgresql, what other options?
> 

MySQL.  We've tried a few different configs with both test=oltp and 
test=threads, but both show the same behavior.  What I have settled on 
for my repro is the following:

sudo sysbench --db-driver=mysql --mysql-host=localhost --mysql-user=root 
--mysql-db=test1 --max-time=180 --max-requests=100000000 --num-threads=8 
--test=oltp prepare
sudo sysbench --db-driver=mysql --mysql-host=localhost --mysql-user=root 
--mysql-db=test1 --max-time=180 --max-requests=100000000 --num-threads=8 
--test=oltp run

Have also some environments where multiple sysbench instances are run 
concurrently (I've tried up to 8, with db's test1-8 being specified), 
but doesn't appear to much matter either.

  - Eric