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Re: GC (was: lists.texi)

From: Luc Teirlinck
Subject: Re: GC (was: lists.texi)
Date: Fri, 24 Jun 2005 18:52:21 -0500 (CDT)

Juri Linkov wrote:

   In my tests, when I have the default gc-cons-threshold set to 400000,
   GC takes 1 sec.  When I increase it 100 times to 40000000, GC takes
   the same 1 sec (and not 100 sec as if there were linear dependence).
   And there is no slowdown.

Increasing gc-cons-threshold by a factor of 10 to 4M indeed produced a
marked speedup in my artificial tests.  My machine is too fast to
notice slowness problems due to CPU usage during actual Emacs use,
except in the case of outright bugs.

   Could you tell all disadvantages? (except of obvious one of memory use
   which users with large memory can tolerate).

Well, obviously if you have very little resident memory and set
gc-cons-threshold to a huge value, then conceivably your operating
system could wind up spending most of its time swapping memory.  Then
not only Emacs, but everything else as well, will become slow.  I do
not know whether that is what Eli is referring too.  Certainly, if you
have a reasonable amount of resident memory, increasing
gc-cons-threshold to 4M should not create any such problems and it
does speed up things.



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