[Flask] uWSGI and Flask - Slow and varying response times

[Unai Rodriguez]

What happened to the inconsistent timings though?

-- unai

On Thu, Jul 7, 2016, at 05:35 PM, Unai Rodriguez wrote:
> Fantastic collaborative effort!!! :) 
> 
> -- unai
> 
> On Thu, Jul 7, 2016, at 02:42 PM, Ziirish wrote:
> > Hello,
> > 
> > I think you have your answer right with the last piece of information you
> > gave us.
> > 
> > Your CPU clock is two times faster than your servers one.
> > 
> > Now your code is probably not multi threaded, it means your server will
> > perform at least two times slower than your development machine to
> > execute the same piece of code.
> > 
> > The x3 you are measuring is probably due to some context switch or
> > something (your kernel is probably spitting the task in several pieces to
> > let other processes perform well so these pieces of processes then need
> > to be synced or something)
> > 
> > In conclusion, the delay you are observing is due to a lower CPU clock on
> > the server. So unless you can multi thread your application there's not
> > much to do.
> > In the other hand, because you have a lot of cores, your server will be
> > able to serve (at least) 8 simultaneous clients within the same time
> > range.
> > 
> > You can also have a look at PyPy as already suggested to try to optimize
> > the generated "bytecode". It can probably save you a few CPU cycles and
> > thus decrease your whole compute time.
> > 
> > 
> > 
> > 
> > Le 7 juillet 2016 05:40:30 GMT+02:00, Tim van der Linden <tim at shisaa.jp>
> > a écrit :
> > >On Wed, 06 Jul 2016 18:28:15 +0800
> > >Unai Rodriguez <unai at sysbible.org> wrote:
> > >
> > >> Hi Tim,
> > >
> > >Hi Unai
> > >
> > >> For uwsgi/Python you could do the same, build a simple page and a
> > >more
> > >> complicated one and compare (no database queries to isolate).
> > >
> > >First a simple page on uWSGI using Flask and Jinja. The template only
> > >consists out of the bare minimals for a HTML page and a single string
> > >variable to be printed and the whole application is a single Python
> > >file with only one view. The timings are done using the Werkzeug
> > >profiler:
> > >
> > >Local: 7 ms for initial request, 0.5ms for all following requests
> > >Server: 160 ms for initial request, 1ms for all following requests
> > >
> > >I will count that as identical. The Snakeviz graphs also look identical
> > >for both.
> > >
> > >Then I added a few range(1, 1000) loops to be printed in Jinja2 and a
> > >load of simple text:
> > >
> > >Local: 9 ms for initial request, 3 ms for all following requests
> > >Server: 24 ms for initial request, 10 ms for all following requests
> > >
> > >Slowly a difference between the two start to form.
> > >
> > >I added some more elements to the view and template such as a WTF form,
> > >but the timings did not went up much. The difference stayed however:
> > >server being three times slower then local.
> > >
> > >I also added a couple of (fast) database queries in the mix, opening
> > >and closing both cursors and connections per query:
> > >
> > >Local: 16 ms for initial request, 11 ms for all following requests
> > >Server: 51 ms for initial request, 33 ms for all following requests
> > >
> > >> The server/os will have to be looked at some point as well. 
> > >
> > >This was interesting but maybe less important since this is testing
> > >pure CPU throughput:, I yanked a primes Python script of the interwebs
> > >to test the raw processing speed and ran it on both machines.
> > >
> > >Local: 3.3879199028 s
> > >Server: 9.26460504532 s
> > >
> > >This is a script without any extras, one Python function tested with
> > >Timeit and ran directly via the Python CLI. My local machine is three
> > >times faster than the server.
> > >
> > >Installing Sysbench and doing a primers test (20000) outside of Python:
> > >
> > >Local: 18.1605 seconds
> > >Server: 42.1942 seconds
> > >
> > >CPU info:
> > >
> > >Local: 1 x i74790K (4 Ghz)
> > >Server: 8 x Xeon E7-4820 v2 (2 Ghz)
> > >
> > >> -- unai
> > >
> > >Cheers,
> > >Tim
> > >_______________________________________________
> > >Flask mailing list
> > >Flask at python.org
> > >https://mail.python.org/mailman/listinfo/flask
> > 
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