Date: Wed, 19 Nov 2003 00:30:21 -0500 From: Garance A Drosihn <drosih@rpi.edu> To: Robert Watson <rwatson@freebsd.org>, David Schultz <das@freebsd.org> Cc: current@freebsd.org Subject: Re: Unfortunate dynamic linking for everything Message-ID: <p06002033bbe0acb7b8c0@[128.113.24.47]> In-Reply-To: <Pine.NEB.3.96L.1031118233432.99345H-100000@fledge.watson.org> References: <Pine.NEB.3.96L.1031118233432.99345H-100000@fledge.watson.org>
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At 11:45 PM -0500 11/18/03, Robert Watson wrote: > >My feeling is we should all go away for a day or two, and run >our favorite macro-benchmark on our favorite sensitive dynamic >linking-sensitive application. I wish I had the time and background to implement one solution that I'd like to benchmark. have a: chflags ldcache /bin/sh When the loader goes to execute some binary, it checks for this ldcache flag. If set, it checks to see if it already has a cached copy of this program (probably checking based on a key of inode+lastchg for a match). If not, it links and loads the file into memory. It saves away a read-only copy of the result of that load. Then it does the appropriate magic to create a copy-on-write image of the loaded file, and executes that. If it already has a cached copy of that file, well, it just makes another copy-on-write image of the loaded file, and executes that. No I/O, no loading, no linking. Just RAM. Yes, disks have been getting bigger, but so has available memory. I think we would see a MUCH bigger win by taking advantage of that memory, than we will ever see by statically-linking system binaries. On the other hand, I have no idea if the above idea would be easy to implement in FreeBSD. It also needs to be a bit smarter than what I described, to cover the dynamic-library case (eg: the very PAM/NSS issue that we're interested in). If that isn't workable, I'm sure there are other strategies which could be imagined. Strategies which will give us more of a performance boost than static-linking these few programs will give us. -- Garance Alistair Drosehn = gad@gilead.netel.rpi.edu Senior Systems Programmer or gad@freebsd.org Rensselaer Polytechnic Institute or drosih@rpi.edu
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