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Update documentation of pure-space overflow

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* doc/lispref/internals.texi (Garbage Collection)
(Pure Storage):
* src/alloc.c (Fgarbage_collect): Update the documentation of
pure-space overflow for when pdumper is used.  (Bug#38492)
This commit is contained in:
Eli Zaretskii 2019-12-14 20:02:11 +02:00
parent 0eff1a0191
commit a01a722282
2 changed files with 19 additions and 11 deletions
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25
doc/lispref/internals.texi
View file

@ -261,12 +261,17 @@ the memory space can be shared by all the Emacs jobs running on the
machine at once. Pure storage is not expandable; a fixed amount is
allocated when Emacs is compiled, and if that is not sufficient for
the preloaded libraries, @file{temacs} allocates dynamic memory for
the part that didn't fit. The resulting image will work, but garbage
collection (@pxref{Garbage Collection}) is disabled in this situation,
causing a memory leak. Such an overflow normally won't happen unless
you try to preload additional libraries or add features to the
standard ones. Emacs will display a warning about the overflow when
it starts. If this happens, you should increase the compilation
the part that didn't fit. If Emacs will be dumped using the
@code{pdump} method (@pxref{Building Emacs}), the pure-space overflow
is of no special importance (it just means some of the preloaded stuff
cannot be shared with other Emacs jobs). However, if Emacs will be
dumped using the now obsolete @code{unexec} method, the resulting
image will work, but garbage collection (@pxref{Garbage Collection})
is disabled in this situation, causing a memory leak. Such an
overflow normally won't happen unless you try to preload additional
libraries or add features to the standard ones. Emacs will display a
warning about the overflow when it starts, if it was dumped using
@code{unexec}. If this happens, you should increase the compilation
parameter @code{SYSTEM_PURESIZE_EXTRA} in the file
@file{src/puresize.h} and rebuild Emacs.
@ -510,9 +515,11 @@ Total heap size, in @var{unit-size} units.
Heap space which is not currently used, in @var{unit-size} units.
@end table
If there was overflow in pure space (@pxref{Pure Storage}),
@code{garbage-collect} returns @code{nil}, because a real garbage
collection cannot be done.
If there was overflow in pure space (@pxref{Pure Storage}), and Emacs
was dumped using the (now obsolete) @code{unexec} method
(@pxref{Building Emacs}), then @code{garbage-collect} returns
@code{nil}, because a real garbage collection cannot be done in that
case.
@end deffn
@defopt garbage-collection-messages

5
src/alloc.c
View file

@ -6050,8 +6050,9 @@ where each entry has the form (NAME SIZE USED FREE), where:
- FREE is the number of those objects that are not live but that Emacs
keeps around for future allocations (maybe because it does not know how
to return them to the OS).
However, if there was overflow in pure space, `garbage-collect'
returns nil, because real GC can't be done.
However, if there was overflow in pure space, and Emacs was dumped
using the 'unexec' method, `garbage-collect' returns nil, because
real GC can't be done.
See Info node `(elisp)Garbage Collection'. */)
(void)
{