diff options
| -rw-r--r-- | doc/lispref/internals.texi | 13 | ||||
| -rw-r--r-- | etc/NEWS | 7 |
2 files changed, 17 insertions, 3 deletions
diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi index f85c266edef..c52999e1cd2 100644 --- a/doc/lispref/internals.texi +++ b/doc/lispref/internals.texi @@ -533,9 +533,6 @@ be allocated for Lisp objects after one garbage collection in order to trigger another garbage collection. You can use the result returned by @code{garbage-collect} to get an information about size of the particular object type; space allocated to the contents of buffers does not count. -Note that the subsequent garbage collection does not happen immediately -when the threshold is exhausted, but only the next time the Lisp interpreter -is called. The initial threshold value is @code{GC_DEFAULT_THRESHOLD}, defined in @file{alloc.c}. Since it's defined in @code{word_size} units, the value @@ -562,6 +559,16 @@ increases. Thus, it can be desirable to do them less frequently in proportion. @end defopt + Control over the garbage collector via @code{gc-cons-threshold} and +@code{gc-cons-percentage} is only approximate. Although Emacs checks +for threshold exhaustion regularly, for efficiency reasons it does not +do so immediately after every change to the heap or to +@code{gc-cons-threshold} or @code{gc-cons-percentage}, so exhausting +the threshold does not immediately trigger garbage collection. Also, +for efficency in threshold calculations Emacs approximates the heap +size, which counts the bytes used by currently-accessible objects in +the heap. + The value returned by @code{garbage-collect} describes the amount of memory used by Lisp data, broken down by data type. By contrast, the function @code{memory-limit} provides information on the total amount of @@ -2430,6 +2430,13 @@ remote systems, which support this check. ** 'memory-limit' now returns a better estimate of memory consumption. +++ +** When interpreting 'gc-cons-percentage', Emacs now estimates the +heap size more often and (we hope) more accurately. E.g., formerly +(progn (let ((gc-cons-percentage 0.8)) BODY1) BODY2) continued to use +the 0.8 value during BODY2 until the next garbage collection, but that +is no longer true. Applications may need to re-tune their GC tricks. + ++++ ** New macro 'combine-change-calls' arranges to call the change hooks ('before-change-functions' and 'after-change-functions') just once each around a sequence of lisp forms, given a region. This is |