[PATCH 1/3] gitk: turn off undo manager in the text widget

From e965e1deb9747bbc2b40dc2de95afb65aee9f7fd Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Sun, 6 Nov 2016 20:38:03 +0100
Subject: [PATCH 1/3] gitk: turn off undo manager in the text widget

The diff text widget is read-only, so there's zero point in building an undo stack. This change reduces memory consumption of this widget by about 95%.

Memory usage of the whole program for viewing a reference commit before; 579'692'744 bytes, after: 32'724'446 bytes.

Test procedure:

 - Choose a largish commit and check it out. In this case one with
   90'802 lines, 5'006'902 bytes.

 - Have a Tcl version with memory debugging enabled. This is,
   build one with --enable-symbols=mem passed to configure.

 - Instrument Gitk to regularly show a memory dump. E.g. by adding
   these code lines at the very bottom:

     proc memDump {} {
         catch {
             set output [memory info]
             puts $output
         }

         after 3000 memDump
     }

     memDump

 - Start Gitk, it'll load this largish commit into the diff text
   field automatically (because it's the current commit).

 - Wait until memory consumption levels out and note the numbers.

Note that the numbers reported by [memory info] are much smaller than the ones reported in 'top' (1.75 GB vs. 105 MB in this case), likely due to all the instrumentation coming with the debug version of Tcl.

Signed-off-by: Markus Hitter <mah@jump-ing.de>
---
 gitk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)