Date: Fri, 29 Oct 1999 01:13:48 +0200 From: Michael Beckmann <petzi@apfel.de> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Julian Elischer <julian@whistle.com>, hackers@FreeBSD.ORG Subject: Re: Limitations in FreeBSD Message-ID: <19991029011348.B2757@apfel.de> In-Reply-To: <199910282234.PAA12655@apollo.backplane.com>; from Matthew Dillon on Thu, Oct 28, 1999 at 03:34:53PM -0700 References: <199910282143.OAA10601@apollo.backplane.com> <Pine.BSF.4.10.9910281455250.11610-100000@current1.whistle.com> <19991029005450.A2757@apfel.de> <199910282234.PAA12655@apollo.backplane.com>
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On Thu, Oct 28, 1999 at 03:34:53PM -0700, Matthew Dillon wrote: > :OK, so I know now that I can have pretty large files in the Terabyte range. > :Very nice. But I assume I cannot mmap anything like a 100 GB file ? > : > :Michael > > Intel cpu's only have a 4G address space. Your are limited to around > a 2G mmap()ing. You can mmap() any portion of a larger file but you > cannot mmap() the whole file at once. > > The easiest thing to do is to simply create a number of fixed-sized files > and tell CNFS to use them. Here is the problem: When you want to have 500 GB of storage, you will need 250 files. In the current implementation of nnrpd, this will need 250 file descriptors per nnrpd. This will limit the number of readers that can be supported on a system, because a nnrpd is spawned for each reader. I was told that nnrpd can be hacked to only consume file descriptors when really needed, but itīs supposed to have a performance penalty. Thatīs why Iīm looking for a way of having large mmapīable files. Are you saying that ALL Intel CPUs, including PIII, can only address 4 GB? I probably need to look at other architectures or solve this fd problem. Michael To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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