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From:shawn Date:February 5 2015 6:01pm
Subject:Re: Latency question - #of connections
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Hello Learner,

On 2/5/2015 11:40 AM, Learner Study wrote:
> Hello MySQL experts,
> I am new to MySQL and am seeing following behavior
> Setup:
> MySQL 5.6.16 + thread pool extensions running on 3.18 kernel
> Two sysbench clients running from different PCs with total of 14k
> connections, each connection doing 2 select queries per sec.
> When I specify 7k connections from each client, sysbench shows latency
> of .3 msec (for both sides)
> If I run with 13k from one client and 1k from the other, latency comes
> to .6 msec (for both sides)
> I get that we are load balancing with 7k so latency improves but any
> ideas which part of MySQL server I should profile to see which area is
> messing it up with 13k+1k connection split- could it be poll() call?
> Or some other kernel area?
> Thanks in advance for my pointers...
> Martin
> PS: I hear that the same thing when run on kernel 2.6.32 doesn't show
> this bad latency witj 13+1 split...yet to be confirmed though

Which MySQL are you using (who built it, whose version of the source 
code is it built from) ?

Which 'thread pool extensions' do you mean? (a reference URL to the 
appropriate documentation would be useful)

Shawn Green
MySQL Senior Principal Technical Support Engineer
Oracle USA, Inc. - Hardware and Software, Engineered to Work Together.
Office: Blountville, TN