Date: Tue, 23 Mar 2004 20:04:24 -0800 (PST) From: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu> To: Peter Wemm <peter@wemm.org> Cc: freebsd-amd64@freebsd.org Subject: Re: memory allocation question Message-ID: <200403240404.i2O44OOq033215@troutmask.apl.washington.edu> In-Reply-To: <200403231949.41997.peter@wemm.org>
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Peter Wemm wrote: > On Tuesday 23 March 2004 07:25 pm, Steven G. Kargl wrote: > > I may have finally talked my boss into updating my computational > > workstation (which runs FreeBSD). The directions of our computations > > is leading towards massive memory requirement. So, the question is: > > If I have an AMD64 system with 16GB of memory and appropriate kernel > > options, can a single process allocate >15 GB for its use? > > The default malloc limit is 8GB. I picked that arbitarily because it > was double 4GB. It is a tunable that can be changed at boot time. > > However.. mmap() is unlimited. You can use most of the remaining 128TB > of virtual memory for mmap. You could also increase the malloc limit > to nearly 128TB if you wanted to. > > The MAXDSIZ value is where malloc is limited. It defaults to: > #define MAXDSIZ (8192UL*1024*1024) > It can be changed at kernel compile time with 'options MAXDSIZ' or > simply overridden at boot time by setting the tunable kern.maxdsiz. > Thanks, Peter. I knew about MAXDSIZ, but I didn't know if there was some hard limit. I can live with 128TB of virtual memory. I thinking we can start with 16 GB of physical memory in a single node and add nodes to cluster as our memory requirements increase. -- Steve http://troutmask.apl.washington.edu/~kargl/
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