svn commit: r318502 - head/bin/sh

[Jilles Tjoelker]

Author: jilles
Date: Thu May 18 22:10:04 2017
New Revision: 318502
URL: https://svnweb.freebsd.org/changeset/base/318502

Log:
  sh: Keep output buffer across builtins.
  
  Allocating and deallocating repeatedly the 1024-byte buffer for stdout from
  builtins costs CPU time for little or no benefit.
  
  A simple loop containing builtins that write to a file descriptor, such as
    i=0; while [ "$i" -lt 1000000 ]; do printf .; i=$((i+1)); done >/dev/null
  is over 10% faster in a simple benchmark on an amd64 virtual machine.

Modified:
  head/bin/sh/output.c

Modified: head/bin/sh/output.c
==============================================================================
--- head/bin/sh/output.c	Thu May 18 21:44:14 2017	(r318501)
+++ head/bin/sh/output.c	Thu May 18 22:10:04 2017	(r318502)
@@ -254,14 +254,7 @@ flushout(struct output *dest)
 void
 freestdout(void)
 {
-	INTOFF;
-	if (output.buf) {
-		ckfree(output.buf);
-		output.nextc = NULL;
-		output.buf = NULL;
-		output.bufend = NULL;
-	}
-	INTON;
+	output.nextc = output.buf;
 }