Forum OpenACS Q&A: Is OpenACS extremely slow?

A while ago I started experimenting with OpenACS. And while it is
impressive in sofar as the possibilities are concerned, it is
somewhat disappointing in the speed with which everthing is served.

As a webserver I am using an old P200 with a mere 36MB's of EDO RAM.
I know this is very humble as a server, but for it's former purpose
(serving dynamic PHP pages out of a mySQL database off an Apache
webserver) it was perfect and functioned fast and flawless.

However the aolserver / postgresql combination seems to be either
very, very processor intensive or wrongly installed (by me obviously).

Where the mysql and httpd daemons never used more than a few percents
of proc power, aolserver doesn't wake up for less than 20. Postgres
is a little less hungry, but will eat 10 percent off my CPU as well.

This results in extremely slow operation of my OpenACS website, to
the extent that I think of removing it again because it is simply
impossible to work with.

Even when I am NOT using the website (and no-one else is either)
aolserver will eat anywhere between 10 and 20 percent CPU power. When
in use it will fly above 30% (even much higher than this) and
postgres usually does the same when it is used. My whole system
(sshd, proftpd, courier-imap and postfix) seem to suffer from this.

Sorry for the long story, but my questions (after searching the
boards here) are these: a. is this normal behaviour and if not, how
can I tweak my server to operate faster? and b. are there more people
suffering from this?

Sadly, adding a lot more memory is not an option. Besides: I checked another openacs machine here just the other day, and it had a memory footprint of over 250Megs (!). Either the guy who installed that one did something wrong too, or there is some other problem.
I don't get the big difference between aolserver/postgres/openacs and apache/php/mysql by the way. Bot are webservers, combined with a scripting module and a database. Of course, the programs are different, but why should I regard the first as something so much less substantial and resource consuming? What is the big resources hogger in openacs?

I'm pretty new at this, I'm sorry if this is a dumb question, but I'm trying to get this to work and it won't budge!

Sorry about that, I didn't mean to imply there was no configuration problem, you may well need to configure somehting correctly, I merely observered that that is a pretty low mem. level... and it would definately help..

Ok, you asked what the big difference is, so I'll try and explain in general terms.

MySQL is not (arguably) an ACID compliant database. If you're not worried about things like transactional integrity, rollback and so forth, then its fine.... however for the kinds of systems that OpenACS is deployed for these are necessary.

OpenACS is many good things, but perhaps the most significant element is its well conceived datamodel. This extensive arrangement is what offers you the OpenACS facilities such a permissioning, subsite management and so on...

So on that score alone, OpenACS is far more comprehensive (and therefore sizeable) than you existing setup.

Apache Vs AOLServer. This is a more difficult one. It often depend on exactly what you define as Apache (i.e. the numerous extensions). But at the core level Apache offers about 20% of what AOLServer can do. Apache is excellent at serving static pages, simple content and so forth, but AOLServer excels when you need a good, well managed interface to a database and your creating highly interactive web services.

My company has delivered projects on a number of alternative in the past two years (i.e. JBoss/J2EE based, Apache/Tomcat/MySQL, IIS/SQLServer and so forth) and I can tell you, without hesitation or shadow of a doubt, OpenACS is a far superior platform.

And thats not personal evangelism, that comes from the bitter realities of commercial development. I formed our company around OpenACS because it allows us to be highly profitable, deliver with quality whilst at the same time being able to offer our customers fantastic pricing due to reduced development and OS principles.

In fact if anything this is where OpenACS wins over all.. The speed and reliability with which one can create new application is breathtaking....

A recent implementation done with Tomcat/JBoss ended up taking nearly 4-5 times longer than our estimates for an OpenACS based solution.

Looking at your original mail I'm a bit surprised by one thing. You say AOLServer is constantly consuming about 20% of your processing power, even when idle... I can certainly say that in all our installations AOLServer remains quiet and very low in terms of resource usage......

This does seem unusual....

So you have further info on your setup? i.e. what versions of Linux are you using?... Also are you using OpenACS 3 or 4.... if 3 I can't really help you. My comments above all relate to 4.5

It might be worth posting to the AOLServer mailing list, as there's some pretty switched on AOLServer folks there.

Also, and I can't promise I'll know, can you post up your config file for AOLServer (remove passwords ;)....

But in summary, no, I don't think what your seeing is 'normal' so I'm sure someone here will be able to help :)

PS/ Another good reason to use OpenACS, is that this community is one of the best around.

OpenACS is much more RAM intensive than CPU. I run two sites one, Aolserver/tcl and one OpenACS 4.5 on a AMD 500Mhz machine with 256MB ram.

I ran my development server on a sparc 10 (dual 50 mhz!) w/128MB ram.  I'd  consider that pretty close to minimum, memory wise.  (Especially since part was taken up by emacs. :)  Caching all the tcl procs alone was close to 20 MB on a default 3.2.5 install; I imagine 4.x is more.  Move the packages you don't use somewhere else, and get more ram.

I think the main reason to point out here in concern to what is the difference in resource usage between AOLserver/OpenACS vs Apache/PHP is to understand the underlying architecture.

Apache works in a forking model which create/destroy new processes as needed. PHP stores no cache information (in memory ... it does in files) at all so each page execution requires merely the weight in memory of the apache process.

AOLserver/OpenACS on the other hand has hundreds of procs that are compiled into each interpeter and an extensive cache which expands during the course of an aolserver process life to speed up its dynamic execution. The memory allocation scheme of AOLserver is such that any time it needs more memory for potential new cache items it determines if there is any free memory left since last allocation and then if not creates a new block of memory to use until that is used up. This is a *zippy* fast memory allocator but also has a high level mark indicator for its footprint meaning that a process can only grow not shrink over time. According to Amadahl's law the bottleneck of any system determines overall throughput. Since memory is faster than disk it was determined to take advantage of this fact but heavily using the memory of a system to improve performance.

AOLserver was built to handle large load efficiently but requires memory for this. OpenACS adds the datamodel, interface to that model on top of AOLserver speeding application development. You very well could duplicate this architecture on Apache but would require a substantial amount of effort.

Anyway as a side note I did alot of development on an AOLserver/Postgres backed site on a celeron with 32 Meg of RAM couple years ago and worked pretty fast/well if tuned to minimum settings. The extra layer of OpenACS though is too much of a footprint to not use more ram.

Off the topic:

I doubt anyone is screaming... memory help!!!! like me.

I develop on CCM 5.1 + resin + Oracle + eclipse + emacs

So whenever I switch back to OACS + aolserver + postgres + emacs ... I am a very happy dude.

I would like to get back on cgi + mathopd + flatfiles + vi