ivoras at fer.hr
Fri May 12 14:14:22 PDT 2006
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
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?
(This is FreeBSD 6.1-R, 2CPU SMP).
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