Date: Sun, 22 Jun 2003 11:14:44 +0200 From: "Petri Helenius" <pete@he.iki.fi> To: "D. J. Bernstein" <djb@cr.yp.to>, <freebsd-performance@freebsd.org> Subject: Re: ten thousand small processes Message-ID: <003001c3389f$7bb6a9f0$63d6473e@PETEX31> References: <20030621185821.30070.qmail@cr.yp.to>
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Have you looked at the malloc manpage and tuned the cache size; < Reduce the size of the cache by a factor of two. The default cache size is 16 pages. This option can be specified multiple times. > Double the size of the cache by a factor of two. The default cache size is 16 pages. This option can be specified multiple times. Pete ----- Original Message ----- From: "D. J. Bernstein" <djb@cr.yp.to> To: <freebsd-performance@freebsd.org> Sent: Saturday, June 21, 2003 8:58 PM 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 > _______________________________________________ > freebsd-performance@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-performance > To unsubscribe, send any mail to "freebsd-performance-unsubscribe@freebsd.org" >
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