Re: apache-mpm-prefork debian perfomance tuning

[anoop aryal <aaryal@foresightint.com>]

On Tuesday 27 March 2007 08:44, Roberto C. Sánchez wrote:
> On Tue, Mar 27, 2007 at 03:03:11PM +0530, Siju George wrote:
> > Hi,
> >
> > Just wondering for what amount of Load the default configuration of
> > apache2-mpm-prefork in Sarge is tuned?
> >
> > Will it server well about 1,000 users simultaneously?
>
> It depends.  There are so many variables that it is not even funny.

so true.

> You 
> probably want to investigate thouroughly what it is that you are trying
> to do, figure out what packages you will be using and then look at the
> content that you will be serving.  Only then will you even begin to have
> enough information to make something resembling a guess that is within
> an order of magnitude.

even then, to answer a question like "how many simultanious users can the site 
handle" is near impossible. you'd first need to define "simultanious". you 
may begin to attempt to answer a slightly different question of "how many 
visitors per hour" or some such. even then, the best guesstimate would be the 
order of magnitude. simply because there are so many variables involved.

i do stress testing every year or so for a cluster of web servers. "httperf", 
snmp, cactus, rrdb et al. are your friends. enable "response time" logging in 
apache and keep an eye out for pages taking longer than 0 seconds. (afaik, 
apache rounds down to the nearest second). enable slow query logging in 
mysql. then use explain to find out what's causing each 'slow-query' to take 
as long as it does. fill the database with data before doing your tests. the 
database behaves differently with a lot of data vs. without (eg. mysql uses 
table scans even when there are indexes when it figures it has to look at 75% 
or the data in the table or some such). and if you do end up using a stress 
generator (for the lack of a better term) like 'httperf', make sure you are 
not measuring the performance of the machine generating the requests.

even the smallest delay you would barely notice when not under stress tends to 
magnify and contribute to heavy load on the system when it gets busy. so the 
only way to find out is to really put the system under heavy load using 
httperf or the like..

hope that helps.

>
> To put it in perspective, you have something equivalent to "can a
> roadway handle 100 vehicles?"  Without providing any other information
> to help, it is impossible to answer.
>
> Regards,
>
> -Roberto

-- 

anoop aryal
aaryal@foresightint.com