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[Python-Dev] Re: marking shared-ness
Greg Steingstein@lyra.org
Fri, 21 Apr 2000 12:52:06 -0700 (PDT)
On Fri, 21 Apr 2000, Christian Tismer wrote:>...> > No. Now you're just talking processes with IPC. Yes, they happen to run in> > threads, but you got none of the advantages of a threaded application.>> Are you shure that every thread user shares your opinion?Now you're just being argumentative. I won't respond to this.>...> Other languages have much fewer problems here (I mean> C, C++, Delphi...), they are able to do the right thing> in the right place.> Python is not designed for that. Why do you want to enforce> the impossible, letting every object pay a high penalty> to become completely thread-safe?Existing Python semantics plus free-threading places us in this scenario.Many people have asked for free-threading, and the number of inquiriesthat I receive have grown over time. (nobody asked in 1996 when I firstpublished my patches; I get a query every couple months now)>...> You know that I like to optimize things. For me, optimization> mut give an overall gain, not just in one area, where others> get worse. If free threading cannot be optimized in> a way that gives better overall performance, then> it is a wrong optimization to me.>> Well, this is all speculative until we did some measures.> Maybe I'm just complaining about 1-2 percent of performance> loss, then I'd agree to move my complaining into /dev/null :-)It is more than this. In my last shot at this, pystone ran about half asfast. There are a few things that will be different this time around, butit certainly won't in the "few percent" range.Presuming you can keep your lock contention low, then your overallperformances *goes up* once you have a multiprocessor machine. Sure, eachprocessor runs Python (say) 10% slower, but you have *two* of them going.That is 180% compared to a central-lock Python on an MP machine.Lock contention: my last patches had really high contention. It didn'tscale across processors well. This round will have more fine-grained locksthan the previous version. But it will be interesting to measure thecontention.Cheers,-g-- Greg Stein,http://www.lyra.org/
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