Date: Fri, 1 Jun 2001 11:40:43 -0700 From: David Greenman <dg@root.com> To: "Karsten W. Rohrbach" <karsten@rohrbach.de> Cc: Alexander Langer <alex@big.endian.de>, chat@FreeBSD.ORG, jkh@freebsd.org Subject: Re: NMBCLUSTERS setting in default kernel Message-ID: <20010601114043.L19893@nexus.root.com> In-Reply-To: <20010601203848.J10477@mail.webmonster.de>; from karsten@rohrbach.de on Fri, Jun 01, 2001 at 08:38:48PM %2B0200 References: <20010529214403.L85298@mail.webmonster.de> <20010530205056.G29853@mail.webmonster.de> <20010530210351.C65759@rapier.smartspace.co.za> <20010531233829.A58131@zerogravity.kawo2.rwth-aachen.d> <20010601154523.A10477@mail.webmonster.de> <20010601164222.A4578@zerogravity.kawo2.rwth-aachen.d> <20010601203848.J10477@mail.webmonster.de>
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>Alexander Langer(alex@big.endian.de)@2001.06.01 16:42:22 +0000: >> Well, I'm more interested in some charts, that shows the performance >> of various NMBCLUSTERS values up to - uhm BIG values (> 2^20). >> Knowing these it could be easier to decide what's better for a certain >> usage. >> >> I thought maybe someone has already done >> some, since I could imagine, that a too high value could decrease >> speed again (due to memory utilization overhead). >> >> I'm currently using 2^14, which seems to be a good choice, when I take >> a look at your value. >NMBCLUSTERS=16384 is my default kernel setting on all machines. >it is also my proposition to get this into the default kernel. >larger values like 256k would make the box slower i think. > >jordan: would 16384 make sense or would it kill machines with low mem? NMBCLUSTERS only sets the limit. It has the effect of pre-allocating kernel virtual memory, so setting it arbitrarily high needs to be avoided since it can lead to running out of kernel VM. It's current value defaults to something that is based on the maximum number of processes configured (multiplied times a constant) plus a constant slush amount. The values of both of these could be tweaked, but setting it to a specific value (i.e. disabling the automatic sizing) for all configurations is probably a bad idea. -DG David Greenman Co-founder, The FreeBSD Project - http://www.freebsd.org President, TeraSolutions, Inc. - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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