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    SubjectRe: [ANNOUNCE] Native POSIX Thread Library 0.1
    Buddy Lumpkin wrote:

    >Sun introduced a new thread library in Solaris 8 that is 1:1, but it did
    >not replace the default N:M version, you have to link against
    >/usr/lib/lwp.
    >
    >http://supportforum.sun.com/freesolaris/techfaqs.html?techfaqs_2957
    >http://www.itworld.com/AppDev/1170/swol-1218-insidesolaris/
    >
    >I was at a USENIX BOF on threads in Boston year before last and Bill
    >Lewis was ranting about how the N:M model sucks. Christopher Provenzano
    >was right there and didn't seem to add any feelings one way or the
    >other.
    >
    >Regards,
    >
    >--Buddy
    >
    I heard this a while ago, and talked with someone I knew who had inside
    information about this. According to that person, Sun will be switching
    the default threads library to 1:1 (It looks like from the document
    referenced below it is Solaris 9). In various benchmarks, sometimes M:N
    won, and sometimes 1:1 won, so performance was a wash. The main problem
    was that they could never get certain things to work "just right" under
    an M:N model, the complexity of M:N was just too high to be able to get
    it working 100% correctly. He didn't have specific details, though.

    Having implemented a threads package with prority inheritance, I expect
    that doing that with an M:N thread model will be extremely complex.
    With activations is possible, but that doesn't mean it's easy. It's
    hard enough with a 1:1 model. A scheduler with good "global" properties
    (for example, a scheduler that guaranteed time share to classes of
    threads that occur in different processes) would be difficult to
    implement properly, too.

    Complexity is the enemy of reliability. Even if the M:N model could get
    slightly better performance, it's going to be very hard to make it work
    100% correctly. I personally think the NPT is going in the right
    direction on this one.

    -Corey

    >
    >-----Original Message-----
    >From: linux-kernel-owner@vger.kernel.org
    >[mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Bill Davidsen
    >Sent: Monday, September 23, 2002 12:15 PM
    >To: Peter Waechtler
    >Cc: Larry McVoy; linux-kernel@vger.kernel.org; ingo Molnar
    >Subject: Re: [ANNOUNCE] Native POSIX Thread Library 0.1
    >
    >On Mon, 23 Sep 2002, Peter Waechtler wrote:
    >
    >
    >
    >>Am Montag den, 23. September 2002, um 12:05, schrieb Bill Davidsen:
    >>
    >>
    >>
    >>>On Sun, 22 Sep 2002, Larry McVoy wrote:
    >>>
    >>>
    >>>
    >>>>On Sun, Sep 22, 2002 at 08:55:39PM +0200, Peter Waechtler wrote:
    >>>>
    >>>>
    >>>>>AIX and Irix deploy M:N - I guess for a good reason: it's more
    >>>>>flexible and combine both approaches with easy runtime tuning if
    >>>>>the app happens to run on SMP (the uncommon case).
    >>>>>
    >>>>>
    >>>>No, AIX and IRIX do it that way because their processes are so
    >>>>
    >>>>
    >bloated
    >
    >
    >>>>that it would be unthinkable to do a 1:1 model.
    >>>>
    >>>>
    >>>And BSD? And Solaris?
    >>>
    >>>
    >>Don't know. I don't have access to all those Unices. I could try
    >>
    >>
    >FreeBSD.
    >
    >At your convenience.
    >
    >
    >
    >>According to http://www.kegel.com/c10k.html Sun is moving to 1:1
    >>and FreeBSD still believes in M:N
    >>
    >>
    >
    >Sun is total news to me, "moving to" may be in Solaris 9, Sol8 seems to
    >still be N:M. BSD is as I thought.
    >
    >
    >>MacOSX 10.1 does not support PROCESS_SHARED locks, tried that 5
    >>
    >>
    >minutes
    >
    >
    >>ago.
    >>
    >>
    >
    >Thank you for the effort. Hum, that's a bit of a surprise, at least to
    >me.
    >
    >
    >



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