[Zope-dev] Zope and SMP

[Jens Vagelpohl]

hi thilo,

the scaling problem comes from the overhead of switching python threads
when they run on 2 CPUs. one strategy, if your OS allowed it, would be
to force the python process onto a single CPU. sunOS/solaris allows you
to do so if i remember right.

you're a little luckier if you actually run 2 zope instances on the
machine (like i do on an old pentium 166 at home), at least on linux,
which does not allow you to set processor affinity, this will force each
python process onto a single CPU.

what you definitely might want to try is a fix that matt kromer here at
digital creations came up with. the technical background is that python
has a built-in timer that controls how often python checks on all its
threads and, if needed, switches from one to another. if you increase
the interval on this timer you will decrease the number of thread
switches, thereby speeding up your zope installation. to apply it to
your own zope install open z2.py in your zope root directory and add the
following line just before the comment that starts the "Configuration
section" (roughly around line 220):

sys.setcheckinterval(50)

the best number given as argument to setcheckinterval is something you
could find out by benchmarking. 50 is what i use on my site, and
compared to two standard zope 2.1.6 instances running i gained about
100% in speed. this fix is becoming part of zope 2.2.0, as far as i know
it is already in the alpha and brian lloyd decided on 120 as a good
number for starters. again, to see the best results you might want to
try different numbers and benchmark the site with e.g. ab.

hope that helps

jens

----

Jens Vagelpohl		jens@digicool.com
Software Engineer	      www.digicool.com
Digital Creations 	(888) 344-4332

Got Zope?

---- 
 

-----Original Message-----
From: zope-dev-admin@zope.org [mailto:zope-dev-admin@zope.org]On Behalf
Of Thilo Mezger
Sent: Thursday, May 18, 2000 03:21
To: zope-dev@zope.org
Subject: [Zope-dev] Zope and SMP


hi!

yesterday, i have test-driven zope on a dual-pentium smp-machine
running linux 2.2 and i was very disappointed by the results.
the zserver threads are running on both cpu's but it seems to
scale really, really badly. i have only done some very cheap
benchmarking but it seems that a single cpu is faster than 2 cpu's.

but as i said, this is not proper benchmarking (yet).  i wanted to
ask if someone has already tried zope on more than 1 cpu and/or
could point me to a direction where i could find out more about
this subject?

cheers!
thilo


-- 
thilo.mezger@innominate.de
                                                        innominate AG
                                                    networking people
fon: +49-30-308806-0  fax: -77 web: http://innominate.de pgp: /pgp/tm

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