Gnus & garbage collection

Gnus & garbage collection

[Jesper Harder]

Hi!

I tried to set `garbage-collection-messages' to t, and I noticed that
Emacs collects garbage like crazy when performing some Gnus actions.

Here are some timing results that show how it affects performance when
entering a large summary buffer and a server buffer.

This is with the default value of `gc-cons-threshold' (400,000 in Emacs):

  Function Name            Call Count  Elapsed Time 
  =======================  ==========  ============ 
  gnus-topic-select-group  1           94.222058    
  gnus-server-read-server  1           50.094491    

And this is with `gc-cons-threshold' increased to 4,000,000:

  Function Name            Call Count  Elapsed Time 
  =======================  ==========  ============ 
  gnus-topic-select-group  1           54.852086
  gnus-server-read-server  1           27.06671

So, with the default value nearly half of the time is spent in the
garbage collector.

I don't know if it's worth doing something about it -- maybe parts of
the code that are likely to generate large amounts of lisp data should
have `gc-cons-threshold' increased, or maybe people should just increase
it themself if they want a faster Gnus (and memory permits it).

-- 
Cheers,
Jesper Harder

Re: Gnus & garbage collection

[Simon Josefsson]

Jesper Harder <harder@ifa.au.dk> writes:

> And this is with `gc-cons-threshold' increased to 4,000,000:

Right.  Gnus feels much more faster with this.

> I don't know if it's worth doing something about it -- maybe parts of
> the code that are likely to generate large amounts of lisp data should
> have `gc-cons-threshold' increased, or maybe people should just increase
> it themself if they want a faster Gnus (and memory permits it).

I wonder if perhaps the Emacs default should be changed, if it hasn't
been touched in years.  Computers might have gotten more memory since
the default value was set.

Re: Gnus & garbage collection

[Jesper Harder]

jas@extundo.com (Simon Josefsson) writes:

> I wonder if perhaps the Emacs default should be changed, if it hasn't
> been touched in years.  Computers might have gotten more memory since
> the default value was set.

I think the last time it was changed was in Emacs 20.x:

GNU Emacs 18.59.1 of Tue Jul 25 1995 on cache.zk3.dec.com (dec-osf)
gc-cons-threshold's value is 100,000

GNU Emacs 19.28.1 (alpha-dec-osf3.0, X toolkit) 
gc-cons-threshold's value is 100,000

GNU Emacs 20.7.1 (i386-redhat-linux-gnu, X toolkit)
gc-cons-threshold's value is 400,000

Re: Gnus & garbage collection

[Romain FRANCOISE]

Simon Josefsson writes:

> Right.  Gnus feels much more faster with this.

Yes, it does dramatically speed things up. Maybe this should go into the
FAQ or be set as a default setting, since 4000kb of ram is really cheap,
these days.

-- 
Romain FRANCOISE <romain@orebokech.com> | V qba'g trg vg. Jung'f nyy
http://www.orebokech.com/               | gur shff nobhg ebg13?

Re: Gnus & garbage collection

[Simon Josefsson]

Jesper Harder <harder@ifa.au.dk> writes:

> jas@extundo.com (Simon Josefsson) writes:
>
>> I wonder if perhaps the Emacs default should be changed, if it 
>> hasn't been touched in years.  Computers might have gotten more 
>> memory since the default value was set.
>
> I think the last time it was changed was in Emacs 20.x:
>
> GNU Emacs 18.59.1 of Tue Jul 25 1995 on cache.zk3.dec.com 
> (dec-osf) gc-cons-threshold's value is 100,000

Available memory in machines have probably increased more than 4 
times since 1995.  The XEmacs default seem to be 500,000.