High load issue, need help

enormoustrousers · 12-08-2006, 08:03 AM

I am experiencing the same high wait problem. Most of the time I have a wait around 97% but every so often it will drop to 15% and apache will suddenly consume ~70% of the resources. Any thoughts? Does this sound familiar to anyone? If apache is the problem, how -- without iostat (I don't have it) -- can I determine which part of apache is the bottleneck?

Thanks

codeguy · 12-10-2006, 01:35 PM

I'd guess your problem is not using indexes for your queries so mysql is doing table scans.

If you get a lot of requests they will all bunch up in a trafic jam waiting for mysql.

Try loggin slow queries. (or pull out some query's and run run them like "describe select * from xtable where key = 'something'" and make sure they are using indexes)

-Andy

enormoustrousers · 12-10-2006, 11:41 PM

Yes, MySQL was my first thought as well. Many of the tables were missing indexes so I went back and created them. This helped a bit as did increasing the number of permitted connections and enabling the query cache (yes, MySQL was set up very poorly.) While that did help, Apache (and sometimes qmail) still tends to hog all the system resources. Any other thoughts as to what would cause such a backup?

Thanks

codeguy · 12-11-2006, 12:54 PM

do you have php/something script that apache is running? Does the script do disk io? (load text files? anything?)

If you have iowait times, then, if you think about it, what processes are doing a lot of disk stuff?

-Andy