Date: 29 Jan 2003 13:28:09 -0700 From: James Gritton <gritton@iserver.com> To: freebsd-hackers@FreeBSD.ORG Subject: Re: What's the memory footprint of a set of processes? Message-ID: <x7k7gnog4m.fsf@guppy.dmz.orem.verio.net> In-Reply-To: Julian Elischer's message of "Wed, 29 Jan 2003 11:45:28 -0800 (PST)" References: <Pine.BSF.4.21.0301291145030.25856-100000@InterJet.elischer.org>
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Julian Elischer <julian@elischer.org> writes: > check out /proc/<PID>/map for a really detailed map of the process. That looks good for a single process, suffers from the problem I'm having. For example, if I run a program that simply mallocs a chumk of memory and reads through it (to map it all in), it's pretty easy to identify the affected object: guppy% cat /proc/23072/map 0x8048000 0x8049000 1 0 0xcdd610c0 r-x 1 0 0x0 COW NC vnode 0x8049000 0x804a000 1 0 0xce619060 rw- 2 0 0x2180 NCOW NNC default 0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x2180 NCOW NNC default ... But after sleeping for a bit, the program then forks, and I have two processes sharing the same memory. I hope to see something that reflects this, but: guppy% cat /proc/23072/map 0x8048000 0x8049000 1 0 0xcdd610c0 r-x 2 0 0x0 COW NC vnode 0x8049000 0x804a000 1 0 0xcdc84360 rw- 2 0 0x180 COW NC default 0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x180 COW NC default ... guppy% cat /proc/23074/map 0x8048000 0x8049000 1 0 0xcdd610c0 r-x 2 0 0x0 COW NC vnode 0x8049000 0x804a000 1 0 0xcdc84360 rw- 2 0 0x180 COW NC default 0x804a000 0xc04b000 16385 0 0xce619060 rwx 2 0 0x180 COW NC default ... The object's ref_count hasn't changed, which is what I meant about seeing reference counts in the kernel that were apparently not counting what I'm looking for. I did see a ref_count increase on the first object (presumably the text image), but nothing on the allocated memory. It seems the object level isn't fine enough, but the deeper I go into the VM code, the more confused I become. In this forked process example, what happens when I alter a few COW pages in the currently-shared object? Apparently a shadow object is created, but it claims to be the same size as the original object. True, but I know it's not actually using that many pages, since most of them are still validly shared. System usage numbers tell me this is true, but I can't find what in the process or object data structures reflect this fact. - Jamie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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