Date: Sat, 13 May 2006 02:51:20 +0200 From: Suleiman Souhlal <ssouhlal@FreeBSD.org> To: Ivan Voras <ivoras@fer.hr> Cc: stable@freebsd.org Subject: Re: pagezero again Message-ID: <44652D88.1070408@FreeBSD.org> In-Reply-To: <4464FA8D.5060309@fer.hr> References: <4464FA8D.5060309@fer.hr>
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Ivan Voras 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? > > (This is FreeBSD 6.1-R, 2CPU SMP). Can you give the output of top(1)? Until this is fixed, you can disable pagezero with sysctl vm.idlezero_enable=0. -- Suleiman
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