apache + php + mysql -> CPU EATING

nyttoc · 04-30-2007, 04:39 AM

hello

i have 10 computers and each of these computers is doing 20 mysql queries (via php) at the same time (simultaneous) every 5 seconds, however i see that apache is eating my CPU sooo much, is that because allow_persistent for mysql is set in php.ini? or what could be the problem with mysql?.. if i don't do a query to mysql with my php file it doesnt eat my cpu... help!

rcase5 · 05-01-2007, 01:38 PM

The answer depends on a lot of things.

What are the specs on these systems? If these systems are Pentiums, I would say that high CPU utilization would be expected under the circumstances you stated. But if they're relatively new Intel Core 2 or AMD Opteron, then that would be a different story.

Also, how big is the database, and what kinds of transactions are being performed? Are these queries updates or inserts, or are there more selects? How complex are the queries? How big is the database? Also, is this database replicated to each of the individual systems or do they reside on one system? If that's the case, the access latency could be a problem.

As for your specific question, I wouldn't think MySQL settings would necessarily affect the amount of CPU Apache takes except for any operations specifically related to MySQL. The 'persistent connections' setting in MySQL is actually designed to improve performance by reducing the need to make new connections every time a web site makes an access to the database. You could try turning off the setting and see if it makes a difference.

nyttoc · 05-02-2007, 03:32 AM

my query is quite simple, but the problem is that 10 computers are accessing my web server at the same time...... Each computer accesses the same php file which is doing a myqsl query and this 20 times simulteneously (i do this for home automation)... so i have about 200 php pages requests at the same time (via AJAX/XMLHTTPREQUEST) to a mysql table, and this causes a huge CPU load of apache. if i don't do a query in that php file i don't have a cpu load so high.. so i think it's normal that my cpu load is so high...

the server has a 1000MHz VIA C3 CPU with 256 MB memory and 500 MB swap file.

fooks · 05-02-2007, 07:58 AM

you may check what mysql is doing at any time:

Code:

# mysqladmin processlist -u root -p
Enter password:

+----+------+-----------+----+---------+------+-------+------------------+
| Id | User | Host      | db | Command | Time | State | Info             |
+----+------+-----------+----+---------+------+-------+------------------+
| 5  | root | localhost |    | Query   | 0    |       | show processlist |
+----+------+-----------+----+---------+------+-------+------------------+