Re: Unfortunate dynamic linking for everything

From: Garance A Drosihn (drosih_at_rpi.edu)
Date: 11/19/03

  • Next message: Chris Shenton: "Re: Recovery? recent "make world" rendered system unusable (64 bit change)" 
    Date: Wed, 19 Nov 2003 00:30:21 -0500
To: Robert Watson <rwatson@freebsd.org>, David Schultz <das@freebsd.org>

    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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  • Next message: Chris Shenton: "Re: Recovery? recent "make world" rendered system unusable (64 bit change)"

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