Date: Sun, 7 Jul 2002 00:07:20 +0200 From: Bernd Walter <ticso@cicely5.cicely.de> To: Darren Pilgrim <dmp@pantherdragon.org> Cc: ticso@cicely.de, freebsd-hackers@FreeBSD.ORG Subject: Re: How does swap work address spacewise? Message-ID: <20020706220720.GG23704@cicely5.cicely.de> In-Reply-To: <3D2762FE.9D9E0378@pantherdragon.org> References: <20020705113532.GA11273@atrbg11.informatik.tu-muenchen.de> <20020705133515.GA295@HAL9000.wox.org> <20020705133837.GA513@HAL9000.wox.org> <20020705234126.GA12183@atrbg11.informatik.tu-muenchen.de> <3D2640A7.3EA2236B@pantherdragon.org> <20020706020656.GL48977@cicely5.cicely.de> <3D2762FE.9D9E0378@pantherdragon.org>
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On Sat, Jul 06, 2002 at 02:37:02PM -0700, Darren Pilgrim wrote: > Bernd Walter wrote: > > On Fri, Jul 05, 2002 at 05:58:15PM -0700, Darren Pilgrim wrote: > > > If RAM + swap can be more than 4GB, how does FreeBSD address swap on a > > > 32-bit machine? Does the kernel internally use a wider address space > > > > The same way it does on every partitition: using block numbers. > > That way you can address 1TByte. > > I thought the limit for filesystems was 2TB? The Blocknumber is signed that gives: 2^31 * 512Bytes > > And you can have more than a single swap partition. > > Up to four, so then the theoretical limit for swap is 8TB? 4 is just a default. [61]cicely9# swapinfo Device 1K-blocks Used Avail Capacity Type /dev/da1b 105472 80 105392 0% Interleaved /dev/da11b 174880 0 174880 0% Interleaved /dev/da4b 211456 0 211456 0% Interleaved /dev/da5b 211456 0 211456 0% Interleaved /dev/da6b 211456 0 211456 0% Interleaved /dev/da7b 211456 0 211456 0% Interleaved /dev/da8b 211456 0 211456 0% Interleaved /dev/da9b 211456 0 211456 0% Interleaved /dev/da10b 211456 0 211456 0% Interleaved Total 1760544 80 1760464 0% The limit here is the maximum number of harddisks, which is IIRC 512 per driver. This cames from the available minor bits in the device node. > > In reality managementstructures which have to be in kernel addressspace > > is limiting swap before. > > Do these management structures grow as swap grows, or do they only > change as the utilization increases? AFAIK there is a static part. Possible not memory but only KVM addressspace. Also AFAIK it makes a difference if you allocate the same space using a single partition or in more than one. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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