RE: ten thousand small processes
From: Pedram Nimreezi (Support_at_Netflag.Net)
Date: 06/22/03
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Date: Sun, 22 Jun 2003 04:45:39 -0700 To: freebsd-performance@freebsd.org
I'm sure Professor Bernstein wouldn't have a problem doing so.
However, I think he's implying a gross oversight...
At 03:50 AM 6/22/2003 -0400, Michael E. Conlen wrote:
>If your going to get this serious about your memory management, couldn't you
>just brk yourself and manage it your self? You seem to know exactly what
>your looking for and expect a specific result. I wouldn't recommend it to
>most, but you seem to know what your doing.
>
>--
>Michael Conlen
>
>-----Original Message-----
>From: owner-freebsd-performance@freebsd.org
>[mailto:owner-freebsd-performance@freebsd.org]On Behalf Of D. J.
>Bernstein
>Sent: Saturday, June 21, 2003 2:58 PM
>To: freebsd-performance@freebsd.org
>Subject: ten thousand small processes
>
>
>FreeBSD 4.8. Test program: malloc(360); malloc(80); malloc(180);
>malloc(16); malloc(440); sleep(10); _exit(0). Compile statically.
>
>The program ends up with 44KB RSS. Where is all that DRAM going? The
>program also ends up with 168KB VSZ. Where is all that VM going?
>
>I don't care much about the 3-page text segment. But I do care about the
>39 extra pages of VM, and the 8 extra pages of DRAM. There's no obstacle
>to having a small program fit into _one_ page per process; two or three
>can be excused, but 39 is absurd. (Yes, I know that Solaris is worse.)
>
>At least 2 pages appear to be wasted by exit(), because it brings in a
>chunk of stdio, which uses 84 bytes of data and 316 bytes of bss. The
>libc implementors clearly don't care about 316 bytes of memory, so why
>don't they make those 316 bytes static? Why doesn't the compiler
>automatically merge some bss into data when that saves a page? Why can't
>I omit exit(), manually or automatically, when it's unreachable?
>
>Furthermore, malloc() appears to chew up a whole new page of DRAM for
>each allocation, plus another page---is this counted in VSZ?---for an
>anonymous mmap. Would it really be that difficult to fit 1076 bytes of
>requested memory into the 3000-odd bytes available at the end of bss?
>
>I sure hope that there's some better explanation for the remaining 32
>pages than ``Well, we decided to allocate 131072 bytes of memory for the
>stack,'' especially when I'm hard-limiting the stack to 4K before exec.
>
>---D. J. Bernstein, Associate Professor, Department of Mathematics,
>Statistics, and Computer Science, University of Illinois at Chicago
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