Hello,

I have a few VPSes with centos5 on which I expirience a strange phenomen:

Every now and then a random network communicating process (lynx, sendmail, httpd, ...) starts eating 100% of cpu while doing nothing. That slows down a VPS a lot.

When examined with lsof, all of such processes have at least one tcp connection in close_wait state. Touching such process with strace -p makes it spring back to life and it goes on working normaly. Sendmail straces are specialy interesting, because I can see it wants to continue smtp dialogue somewhere from the middle. I suspect the cpu usage I see is the process trying to read from tcp socket to which the other end has nothing more to write. But as this is not happening in userspace (where I would see recv() in strace output), I expect the problem lies higher, in virtuozzo.

I would like to be able to understand what is going on and maybe be able to reproduce the problem, but I don't have enough understanding of what exactly goes on. Specifically, what does strace do to a process that knocks it out of the cpu consuming loop?

I'd be happy if you can give me some pointers.