Date: Sat, 16 Mar 2002 11:45:05 -0600 (CST) From: mark tinguely <tinguely@web.cs.ndsu.nodak.edu> To: freebsd-questions@FreeBSD.ORG, jules@aasp.net Subject: Re: 3GB address space for user app's with FreeBSD 4.5 Message-ID: <200203161745.g2GHj5n39237@web.cs.ndsu.nodak.edu> In-Reply-To: <008101c1ccf2$dc569be0$1800a8c0@verizon.net>
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> Out of the box, I can malloc almost 512M. Nice for starter's, but not = > nearly enough. To overcome this (in earlier editions of FreeBSD), I set = > MAXDSIZ and DFLDSIZ to 1.5GB, giving me an effective 1GB of malloc'able = > space. > > But I've made some changes to my application and I need to go higher, at = > least to 2GB, and I would not be surprised in six months to be at 2.5GB. > you are hitting the limit of the IA-32 VM address space of 4G. By default (alittle less than) 3G is available user VM space and 1G of kernel VM space. you could put the kernel VM back to .5G (like it was in the pre FreeBSD 4.x), but you most likely have some problems trimming back the kernels space needs, esp if you have lots of physical memory. There are features in the IA-32 family to expand physical memory to 64GB but the VM is still limited to 4GB. This 4GB VM limitation has been the main reason that many of us do not bother adding the extended physical RAM support in FreeBSD. If your trend is continuing, you will start to need a 64 bit chipset and OS. The Alpha is has extended VM addressing now under FreeBSD. There is the Itanium (IA-64) down the road, or the more promising AMD "Hammer" chipset (which is a Pentium-class chipset with a 64 bit MMU and some additional registers). As an aside comment, it is good enough idea (and the Itanium has not sold well yet), to make Intel start a Pentium-64 project of their own. I hope they support 8KB pages (-- hint, hint Intel). (end of aside comment). --mark tinguely. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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