I had a very odd issue today. Certain php files that shouldn't have taken up too much processing power we're using 75% of a duel xeon (linux) server...
I'm totally at a loss, because the code (vBulletin's showthread, forumdisplay, and newreply), is fairly innocuous, and it seems to me that if it were indeed something processor intensive with the code itself, it should suck that much power EVERY time it's run. But the times it sucked the power were in small corners of my forums that get like 1 view every couple hours, whereas the more heavily trafficked forums and threads were fine.
I suspect that it was a problem with the server itself, and not with the code, but I don't know enough about servers to explain why a little script used by one person sucked up so much power.
Can someone try to shed some light here? Is there any way for an arbitrary script, regardless of its computational intensity, to suck processing power due to a server error in serving the file?
By the way, I guess I should mention that I recently applied some hacks to my forums, which my server admin is convinced caused the problems. However, I have reviewed the hacks and the files, and determined that there were no changes that could possibly suck a substantial amount of processor power about and beyond the original files. In addition to that, the hacks have been applied for about a week, so it should have acted up a week ago. So, it's a vague possibility, but I seriously doubt it.
Im not shure if it has anything to do with it, but one of our host's servers got bogged down with phpBB because we applied a login script that wasnt closing the connections after you logged out etc so the MySQL DB was sucking up a load of resources.