(Output from Processes): New var `process-adaptive-read-buffering'.

diff --git a/lispref/processes.texi b/lispref/processes.texi
index 16d7aa96c1d124f4eaf4bebf6daf348c1ba4b7b5..ccf8f76d87ee731a3f489058b1b0ed047f28a816 100644 (file)
--- a/lispref/processes.texi
+++ b/lispref/processes.texi
@@ -929,6 +929,16 @@ process and only then specify its buffer or filter function; no output
 can arrive before you finish, if the code in between does not call any
 primitive that waits.
 
+@defvar process-adaptive-read-buffering
+On some systems, when Emacs reads the output from a subprocess, the
+output data is read in very small blocks, potentially resulting in
+very poor performance.  This behaviour can be remedied to some extent
+by setting the variable @var{process-adaptive-read-buffering} to a
+non-nil value (the default), as it will automatically delay reading
+from such processes, thus allowing them to produce more output before
+Emacs tries to read it.
+@end defvar
+
   It is impossible to separate the standard output and standard error
 streams of the subprocess, because Emacs normally spawns the subprocess
 inside a pseudo-TTY, and a pseudo-TTY has only one output channel.  If