Date: Fri, 12 May 2006 23:13:49 +0200 From: Ivan Voras <ivoras@fer.hr> To: stable@freebsd.org Subject: pagezero again Message-ID: <4464FA8D.5060309@fer.hr>
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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? (This is FreeBSD 6.1-R, 2CPU SMP).
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