Will Python 3.0 remove the global interpreter lock (GIL)

Terry Reedy tjreedy at udel.edu
Thu Sep 20 02:08:59 CEST 2007

"Terry Reedy" <tjreedy at udel.edu> wrote in message 
news:fcq352$u0a$1 at sea.gmane.org...
| "TheFlyingDutchman" <zzbbaadd at aol.com> wrote in message
| news:1190164166.378500.155990 at o80g2000hse.googlegroups.com...

| Since Guido wrote that, there have been put forth more ideas and interest
| and promises of efforts to remove or revise the GIL or do other things to
| make using multiple cores easier.  (The later being the point of the
| concern over GIL.)

A few days ago, an undergraduate posted on the dev list that he just 
started an independent study project on removing the GIL.  Maybe we'll get 
a report early next year.

Guido also said that he is willing to make changes to the CPython internals 
to aid multiproccessor usage [as long, presumably, as it does not cut speed 
in half].

|| How much faster/slower would Greg Stein's code be on today's
|| processors versus CPython running on the processors of the late
|| 1990's?
| Perhaps a bit faster, though processor speeds have not increased so much
| the last couple of years.

This assumes that comparing versions of 1.5 is still relevant.  As far as I 
know, his patch has not been maintained to apply against current Python. 
This tells me that no one to date really wants to dump the GIL at the cost 
of half Python's speed.  Of course not.  The point of dumping the GIL is to 
use multiprocessors to get more speed!  So with two cores and extra 
overhead, Stein-patched 1.5 would not even break even.

Quad (and more) cores are a different matter.  Hence, I think, the 
resurgence of interest.

||And if you decide to answer, please add a true/false response
|| to this statement - "CPython in the late 1990's ran too slow".
| False by late 1990's standards, True by today's standards ;-).

So now this question for you:  "CPython 2.5 runs too slow in 2007: true or 

If you answer false, then there is no need for GIL removal.
If you answer true, then cutting its speed for 90+% of people is bad.

| Most people are not currently bothered by the GIL and would not want its
| speed halved.

And another question: why should such people spend time they do not have to 
make Python worse for themselves?

Terry Jan Reedy

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