how much memory?

how much memory?

[Joe Corneli]

Sorry about the potential lack of specificity of this question,
but how much memory should I assume Emacs has available to it?

If I'm reading files into buffers or storing them as strings or
something like this, how many characters can I store before I should
expect a crash or other weird behavior.

I've seen the "Memory Usage" node in the elisp manual, but can you
give suggestions on how to extrapolate from there to answer the above
question?

I realize this may depend on hardware and configuration details, but
what's the general algorithm?

Re: how much memory?

[Eli Zaretskii]

> From: Joe Corneli <jcorneli@math.utexas.edu>
> Date: Wed, 24 Aug 2005 00:10:06 -0500
> 
> If I'm reading files into buffers or storing them as strings or
> something like this, how many characters can I store before I should
> expect a crash or other weird behavior.

Why worry?  Emacs gives you a fair warning when it has used up 85% of
the available memory.  Until then, there's nothing to worry about.

Re: how much memory?

[Pascal Bourguignon]

Joe Corneli <jcorneli@math.utexas.edu> writes:
> Sorry about the potential lack of specificity of this question,
> but how much memory should I assume Emacs has available to it?

Sur linux, type: C-u M-! free RET

For example, on my computer, I can asume that emacs has 826164 KB
available for it (if no other program takes it before).

             total       used       free     shared    buffers     cached
Mem:       1031584    1018268      13316          0      62420     573300
-/+ buffers/cache:     382548     649036
Swap:      1004020     178856     825164 <--- maximum memory size available.


> If I'm reading files into buffers or storing them as strings or
> something like this, how many characters can I store before I should
> expect a crash or other weird behavior.

This is something else.  The size of buffer is limited by the
amplitudes of fixnums.  It depends on the version of emacs and the
compilation obptions (32-bit, 64-bit, etc).

See this variable: most-positive-fixnum
On my emacs "22.0.50.1", it's 268435455 = 256 MB
(IIRC on the 21.3 I used it was 128 MB).

Emacs doesn't crash!  It contains very little C, so there's very
little reason to have it crash.  When the buffer becomes full to do
something, it tells you so and that's all.


> I've seen the "Memory Usage" node in the elisp manual, but can you
> give suggestions on how to extrapolate from there to answer the above
> question?

I don't think these statistics are relevant to your question.


> I realize this may depend on hardware and configuration details, but
> what's the general algorithm?


-- 
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
__Pascal Bourguignon__                     http://www.informatimago.com/

Re: how much memory?

[Kevin Rodgers]

Pascal Bourguignon wrote:
 > Emacs doesn't crash!  It contains very little C, so there's very
 > little reason to have it crash.

The 21.x source distribution includes almost 9.9 MB of C code, which
compiled into a 2.2 MB stripped temacs executable on my platform (plus
0.3 MB of lib-src utilities).  That compares to 22.7 MB of Emacs Lisp
and 15.7 MB of byte-compiled Lisp in the distribution, of which 2.6 MB
was dumped into the 4.8 MB emacs executable.  So a fresh emacs is about
46% C and 54% Lisp.

-- 
Kevin Rodgers