Benchmarks

[William Lovaton]

Hi Chris,

El vie, 30-04-2004 a las 10:42, Chris Davies escribió:
> > My load average is between 6 and 20 (25 under xtreme load)
> 
> load is the average number of jobs in the queue over the last minute,
> five minutes and 15 minutes.  I have never seen my tux machine get over
> .8 -- even when serving 60mb/sec.
> 
> I don't really think load average is a very good number other than a
> rough generalization.  I've been on machines where the average is at 1.5
> and the machine is as slow as mud, and I've been on machines where the
> load was 20 and it was still lightning quick.  Other numbers seem to be
> better indications of performance and bottlenecks.

Load average is a good number to look at.  The thing is that a 1.5 load
means there are almost 2 processes in execution state.  It doesn't mean
that you have only 2 users concurently.  If a PHP process is connecting
to the database (or any other kind of I/O) it will be sleep and won't be
counted as a running process... However the web application is still
"executing" and hence the perception of "slowness".

A high load means that there are processes ready to be run but the OS
can't run them because the CPU is busy. Eg: Number of runnable processes
is bigger than the number of processors.

> 
> However, hearing that your load is that high, I would say that something
> is causing you to fork processes frequently.  Does the machine run heavy
> cgi?

It runs PHP as an Apache module _not_ as an CGI.  But yeah, it could be
considered heavy due to the number of users.

It forks processes sometimes, but it is not often due to the Min/Max
Spare Servers directive.  560 users represents about 40 Apache/PHP
processes in the web server.  And in peak load in can reach 80 but this
is not common.

Before, without TUX it reached 250 processes (the max limit) easily...
so TUX is really a magic thing.

> > This is a big enterprise app, highly trasactional.  Right now is serving
> > 550 concurrent users.
> Not too bad.  I've got a few machines that apache claims it needs more
> than MaxClients 1500 -- and no, I don't run keepalive.

I have MaxClientes 100, very low I know but I dont seem to need more.

> 
> > > Machine is pushing 25.34mb/sec
> > How do you get this number??  (25.34mb/sec)
> right off the switch port.

Neat!  I'll talk with the net guy here.  ;-)


-William