Date: Thu, 30 Jan 2003 18:49:52 -0800 From: David Schultz <dschultz@uclink.Berkeley.EDU> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: James Gritton <gritton@iserver.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: What's the memory footprint of a set of processes? Message-ID: <20030131024952.GA11372@HAL9000.homeunix.com> In-Reply-To: <200301310023.h0V0NqAE090963@apollo.backplane.com> References: <Pine.BSF.4.21.0301291145030.25856-100000@InterJet.elischer.org> <x7k7gnog4m.fsf@guppy.dmz.orem.verio.net> <20030130064448.GA7258@HAL9000.homeunix.com> <200301300719.h0U7JOfI086054@apollo.backplane.com> <20030130091419.GA7776@HAL9000.homeunix.com> <200301301923.h0UJNT0l089037@apollo.backplane.com> <20030131001436.GA10856@HAL9000.homeunix.com> <200301310023.h0V0NqAE090963@apollo.backplane.com>
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Thus spake Matthew Dillon <dillon@apollo.backplane.com>: > :Thanks for the explanations! I still don't understand why this > :doesn't work, assuming you don't care about nonresident pages: > : > :for each process p in the set > : for each map entry e in p->vmspace->vm_map > : for each page m in e->object.vm_object->memq > : if I haven't seen this m.phys_addr yet in the scan > : resident_pages++ > > That would get close, as long as the machine is not paging heavily. > Think of it this way: If you have a lot of ram the above calculation > will give you an upper bound on memory use, but some of the pages > in the VM object's may be very old and not actually under active > access by the process (for example, the pages might represent part > of the program that was used during initialization and then never used > again). If you do not have so much memory older pages will get flushed > out or flushed to swap and the above calculation will represent more > of a lower bound on the memory used by the group of processes. Yes, I understand this; that's why I said ``assuming you don't care about nonresident pages'' (a pretty big assumption, mind you.) I was just thinking about essentially calculating the physical memory usage for a set of processes, taking sharing into account, and I take it you were talking about calculating the total amount mapped. I imagine both metrics would be useful. For instance, a database might map a huge file but have a very small resident set. I don't know what the OP intended... To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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