Linux Page Cache y pdflush:
POSIBLES CAUSAS DE HIGH SERVER LOAD
After a month of problems the problem with the high io wait showed up again. This time the problem did not disappear. The server was so slow I couldn’t move the accounts to another server.
I did every possible check (harddisk, motherboard, memory, file sysytem) but didn’t find anything until I did my final effort, switching the network controller. All of a sudden the problem was gone. Everything works ok now.
Sometimes you have to look really hard; Here a list off possible causes of high server loads:
- High server loads could be caused by just one or several resource-intensive application(s). Examples include very high-traffic Web sites, database-driven Web sites, forums, gaming sites, file download sites and so on.
- A high server load can also be caused by a malicious script or a “runaway script” which can continuously loop, dragging down the server’s resources.
- Too many websites on the one server – with the cumulative resources resulting in high server load.
- Running out of memory and swapping to the swap file.
- Server backups or server updates are taking place.
- Mis-configured software causing errors.
- Users sending large mailing lists.
- Users trying to bounce spam.
- Users/spammers sending spam email.
- Hardware issues including memory leak, bad hard drive, and network card.
Try to optimize your drive(s) as much as possible. Are they PATA, SATA, or SCSI? If they’re PATA, use hdparm to set the best possible settings for the drives and your chipset.
You’ll also need to look for the processes that require the resources and why they’re not getting them. You might also want to renice MySQL server to -10 if you’re running it. This gives it more priority so it can do it’s thing faster, but still less priority that vital system processes.
Also view “dmesg” “ps auxwww” “free” “netstat -vap”
Also you may check “dstat -cd -f” or “hdparm -tT” if it’s CentOS.