Date: Mon, 18 Jun 2001 10:55:45 -0700 From: David Greenman <dg@root.com> To: Matt Dillon <dillon@earth.backplane.com> Cc: "Ashutosh S. Rajekar" <asr@softhome.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: max kernel memory Message-ID: <20010618105545.G19893@nexus.root.com> In-Reply-To: <200106181757.f5IHvKK16658@earth.backplane.com>; from dillon@earth.backplane.com on Mon, Jun 18, 2001 at 10:57:20AM -0700 References: <Pine.LNX.4.21.0106181749030.1209-100000@vangogh.indranetworks.com> <200106181757.f5IHvKK16658@earth.backplane.com>
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> >:Hi, >: >:I'm trying to give the kernel (4.0-RELEASE) 2Gb of memory to work with. I >:can afford to have 4Gb of physical memory on one of my servers, and hence >:the experiments. >: >:Is it safe to play around with KERNBASE, and get away without breaking >:code ? Is there any other advisable method if this one is risky ? >: >:-ASR > > Yes, you can change KERNBASE. I'm not entirely sure but I believe if > you have an old set of bootblocks you may have to reinstall them to > get a set that is kernbase-agnostic. e.g. the disklabel -B command on > the appropriate slice. > > DG changed KERNBASE a while back to reserve a gigabyte of VM for the > kernel. This should be sufficient on a 4G machine but it depends where > your resources are going. If your server's resources are user-process > centric then you don't need to change KERNBASE. If your server's > resources are network-mbuf centric then you may have to give the kernel > more KVM (e.g. like 2GB instead of 1GB... 0x80000000 instead of > 0xC0000000). But be careful. The more KVM reserved for the kernel, the > less VM is available for user processes to allocate and mmap. > > I'm sure people who run 4G machines can give you better information, I've > never run anything larger then 2G myself, though expect down the line > I'll begin needing 4G machines to support larger databases. Don't forget to also change NKPDE as well when relocating the start of kernel VM. For kernbase = 0x80000000 on a non-SMP machine, NKPDE needs to be 511. -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-hackers" in the body of the message
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