Subject: Re: sysbench throughput degradation in 4.13+
To: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>,
        =?UTF-8?B?546L6YeR5rWm?= <jinpuwang@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        "KVM-ML (kvm@vger.kernel.org)" <kvm@vger.kernel.org>,
        vcaputo@pengaru.com, Matthew Rosato <mjrosato@linux.vnet.ibm.com>
References: <95edafb1-5e9d-8461-db73-bcb002b7ebef@linux.vnet.ibm.com>
 <CAD9gYJJ9nSAbznEn80hfY3=+YjA8cKw6RztpgW6iDm7rQ0EsFg@mail.gmail.com>
 <50a279d3-84eb-3403-f2f0-854934778037@linux.vnet.ibm.com>
 <20170922155348.zujigkn3o5eylctn@hirez.programming.kicks-ass.net>
From: Eric Farman <farman@linux.vnet.ibm.com>
Date: Fri, 22 Sep 2017 12:12:45 -0400
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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