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On Jan 29, 2015, at 8:57 AM, Roman Podoliaka <rpodolyaka at mirantis.com> wrote:

> Jeremy,
> 
> I don't have exact numbers, so yeah, it's just an assumption based on
> looking at the nova-api/scheduler logs with connection_debug set to
> 100.
> 
> But that's a good point you are making here: it will be interesting to
> see what difference enabling of PyMySQL will make for tempest/rally
> workloads, rather than just running synthetic tests. I'm going to give
> it a try on my devstack installation.


FWIW I tested this a while ago on some perf tests on nova and cinder that we
run internally and I found pymysql to be slower by about 10%. It appears that
we were cpu bound in python more often than we were blocking talking to the
db. I do recall someone doing a similar test in neutron saw some speedup,
however. On our side we also exposed a few race conditions which made it less
stable. We hit a few hard deadlocks in volume create IIRC. 

I don’t think switching is going to give us much benefit right away. We will
need a few optimizations and bugfixes in other areas (particularly in our
sqlalchemy usage) before we will derive any benefit from the switch.

Vish

> 
> Thanks,
> Roman
> 
> On Thu, Jan 29, 2015 at 6:42 PM, Jeremy Stanley <fungi at yuggoth.org> wrote:
>> On 2015-01-29 18:35:20 +0200 (+0200), Roman Podoliaka wrote:
>> [...]
>>> Otherwise, PyMySQL would be much slower than MySQL-Python for the
>>> typical SQL queries we do (e.g. ask for *a lot* of data from the DB).
>> [...]
>> 
>> Is this assertion based on representative empirical testing (for
>> example profiling devstack+tempest, or perhaps comparing rally
>> benchmarks), or merely an assumption which still needs validating?
>> --
>> Jeremy Stanley
>> 
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