Date: Mon, 26 Nov 2007 08:59:12 -0600 From: Guy Helmer <ghelmer@palisadesys.com> To: Gergely CZUCZY <phoemix@harmless.hu> Cc: freebsd-stable@freebsd.org Subject: Re: mmap max size (qemu VM memsize limit) Message-ID: <474ADF40.5050500@palisadesys.com> In-Reply-To: <20071121142404.GA7511@harmless.hu> References: <20071121142404.GA7511@harmless.hu>
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Gergely CZUCZY wrote: > Hello, > > I'm trying to set up a qemu with 4G memory to the host system > on a 7-BETA2, and I've hit some kind of limit in freebsd. > > When i give more then ~2000MB of memory to qemu, it returns > an after trying to mmap() it, saying "Could not map physical memory". > > At the end of mmap(2) there's a note saying: > " The len argument is limited to the maximum file size or available user- > land address space. Files may not be able to be made more than 1TB large > on 32 bit systems due to file systems restrictions and bugs, but address > space is far more restrictive. Larger files may be possible on 64 bit > systems." > > I guess I've found this limit. I've tried to check a few sysctls but I wasn't > able to find the one effecting this limit. > > Could someone point me into the right direction in increasing the maximum > mmap-able size? > > If you are using the 32-bit i386 system, then you could be limited by a couple of things, the kern.maxdsiz loader tunable or the datasize limit are likely. On i386, I believe 1073741824 (1G) is the default maxdsiz. With 4GB of RAM, I think you ought to be able to double kern.maxdsiz in /boot/loader.conf. Hope this helps, Guy -- Guy Helmer, Ph.D. Chief System Architect Palisade Systems, Inc.
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