bug#18522: 24.4.50; mapcar is very slow

[Eli Zaretskii]

> From: Peter Münster <pmlists@free.fr>
> Cc: rudalics@gmx.at,  larsi@gnus.org,  18522@debbugs.gnu.org
> Date: Tue, 23 Feb 2016 17:35:50 +0100
> 
> My current emacs session is running now since 5 hours. The length of the
> chain is 131. And this is my buffer list:
> 
> .%* *Article inbox*        1592 Article          
>  %* *Summary inbox*          85 Summary          
>  %  *Group*                  41 Group            
>  %* *Completions*           180 Completion List  
>     *scratch*               141 Lisp Interaction 
>  %* *Messages*           446718 Messages         
>   * todo.org             147282 Org              ~/todo/todo.org
> 
> I guess, that the slow-down is related to the chain-length. What do you think?

We need to time that loop to be sure.  Can you do that with 'perf', or
add a call to gettimeofday before and after, and see how much time it
takes as the list of buffers grows?

Thanks.