pagezero again

Vlad GALU vladgalu at
Fri May 12 14:27:54 PDT 2006

On 5/13/06, Ivan Voras <ivoras at> wrote:
> Some time ago I reported that pagezero kernel thread sometime takes
> (what seems to me) a too large chunk of available CPU (30%) on a very
> busy web server. There were no replies :( Since then, I've reconfigured
> apache to use PHP as a fastcgi module and the problem seems to have
> gotten worse - now it *always* takes ~25-30% CPU, and my "System" time
> stat shows it (its almost always ~30%).
>  From what I can understand, pagezero thread fills kernel's pool of
> zeroed pages. This looks non-threteaning, but what would cause such high
> demand of zeroed pages on my system? The number of processes is almost
> constant, there are no frequent process spawnings or forks (top shows
> "last pid" to be almost constant). FastCGI processes communicate over
> UNIX sockets.
> Also, pagezero thread is (should be) executing at idle priority - does
> this mean it won't interfere much with machine's performance? Even if
> "0% idle" is not uncommon state?

   How is the system, swapping-wise ?

If it's there, and you can see it, it's real.
If it's not there, and you can see it, it's virtual.
If it's there, and you can't see it, it's transparent.
If it's not there, and you can't see it, you erased it.

More information about the freebsd-stable mailing list