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Re: ObjC configured --with-objc-gc needs external Boehm gc
- To: "Boehm, Hans" <hans_boehm at hp dot com>
- Subject: Re: ObjC configured --with-objc-gc needs external Boehm gc
- From: Helge Hess <helge dot hess at skyrix dot com>
- Date: Wed, 17 Jan 2001 12:16:52 +0100
- Cc: 'Matthias Klose' <doko at cs dot tu-berlin dot de>, gcc at gcc dot gnu dot org,java-discuss at sources dot redhat dot com, ovidiu at cup dot hp dot com
- Organization: http://www.skyrix.com
- References: <140D21516EC2D3119EE700902787664401E3A83E@hplex1.hpl.hp.com>
"Boehm, Hans" wrote:
> > > Does Objective C normally use the collector with thread support?
> > I think that this is 50/50. The problem is that threading currently
> > slows down the runtime to some degree and therefore is often
> > turned off
> > if threading is not required.
> Aside from a tuning problem in current collector versions, it should
> currently cost basically one test-and-set (probably 5-30 cycles depending on
> the processor) on entry, and a store on exit of each malloc call. The
> uniprocessor cost with thread-local allocation (as in GC6.0) is probably
> about the same, though it scales much better on multiprocessors.
I think I wasn't clear. I was referring to the performance of libobjc,
not of the gc. Libobjc gets slower if threading is enabled which is
often the reason why people turn it off.
In this context: How does BoehmGC access threading ? Libobjc has it's
own threading-backend architecture. This might be reused/shared as well
(in one or the other direction).