Re: [PATCH] Speed up "gdb -tui" output

[Pedro Alves <palves@redhat.com>]

On 02/03/2015 06:52 PM, Pedro Alves wrote:

> I'm working on this now.

Turns out that flushing on every line like in my patch was still
considerably (and noticeably) slower than delaying until an explicit
gdb_flush is done, like in Doug's.  So I went with Doug's version.

The recent changes to unify CLI/TUI interface to readline tab
completion made the patch even simpler.  Here's what I pushed
to master.

---
From 518be979d905d8e8708c70149fdb3207aba53aa1 Mon Sep 17 00:00:00 2001
From: Doug Evans <dje@google.com>
Date: Wed, 4 Feb 2015 12:27:28 +0100
Subject: [PATCH] Speed up GDB's TUI output

In the TUI mode, we call wrefresh after outputting every single
character.  This results in the I/O becoming very slow.  Fix this by
delaying refreshing the console window until an explicit flush of
gdb_stdout is requested, or a write to any other (unbuffered) file is
done.

2015-02-04  Doug Evans  <dje@google.com>
	    Pedro Alves  <palves@redhat.com>
	    Eli Zaretskii  <eliz@gnu.org>

	PR tui/17810
	* tui/tui-command.c (tui_refresh_cmd_win): New function.
	* tui/tui-command.c (tui_refresh_cmd_win): Declare.
	* tui/tui-file.c: #include tui/tui-command.h.
	(tui_file_fputs): Refresh command window if stream is not gdb_stdout.
	(tui_file_flush): Refresh command window if stream is gdb_stdout.
	* tui/tui-io.c (tui_puts): Remove calls to wrefresh, fflush.
---
 gdb/ChangeLog         | 12 ++++++++++++
 gdb/tui/tui-command.c | 15 +++++++++++++++
 gdb/tui/tui-command.h |  3 +++
 gdb/tui/tui-file.c    | 10 +++++++++-
 gdb/tui/tui-io.c      |  9 ++++-----
 5 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1116853..d5ec6d1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2015-02-04  Doug Evans  <dje@google.com>
+	    Pedro Alves  <palves@redhat.com>
+	    Eli Zaretskii  <eliz@gnu.org>
+
+	PR tui/17810
+	* tui/tui-command.c (tui_refresh_cmd_win): New function.
+	* tui/tui-command.c (tui_refresh_cmd_win): Declare.
+	* tui/tui-file.c: #include tui/tui-command.h.
+	(tui_file_fputs): Refresh command window if stream is not gdb_stdout.
+	(tui_file_flush): Refresh command window if stream is gdb_stdout.
+	* tui/tui-io.c (tui_puts): Remove calls to wrefresh, fflush.
+
 2015-02-04  Pedro Alves  <palves@redhat.com>
 
 	Fix build breakage.
diff --git a/gdb/tui/tui-command.c b/gdb/tui/tui-command.c
index d1a5ddb..3551063 100644
--- a/gdb/tui/tui-command.c
+++ b/gdb/tui/tui-command.c
@@ -129,3 +129,18 @@ tui_dispatch_ctrl_char (unsigned int ch)
       return c;
     }
 }
+
+/* See tui-command.h.  */
+
+void
+tui_refresh_cmd_win (void)
+{
+  WINDOW *w = TUI_CMD_WIN->generic.handle;
+
+  wrefresh (w);
+
+  /* FIXME: It's not clear why this is here.
+     It was present in the original tui_puts code and is kept in order to
+     not introduce some subtle breakage.  */
+  fflush (stdout);
+}
diff --git a/gdb/tui/tui-command.h b/gdb/tui/tui-command.h
index 8cc5be4..ede2ecc 100644
--- a/gdb/tui/tui-command.h
+++ b/gdb/tui/tui-command.h
@@ -24,4 +24,7 @@
 
 extern unsigned int tui_dispatch_ctrl_char (unsigned int);
 
+/* Refresh the command window.  */
+extern void tui_refresh_cmd_win (void);
+
 #endif
diff --git a/gdb/tui/tui-file.c b/gdb/tui/tui-file.c
index b32cfa6..4b4b92c 100644
--- a/gdb/tui/tui-file.c
+++ b/gdb/tui/tui-file.c
@@ -20,7 +20,7 @@
 #include "ui-file.h"
 #include "tui/tui-file.h"
 #include "tui/tui-io.h"
-
+#include "tui/tui-command.h"
 #include "tui.h"
 
 /* A ``struct ui_file'' that is compatible with all the legacy
@@ -179,6 +179,10 @@ tui_file_fputs (const char *linebuffer, struct ui_file *file)
   else
     {
       tui_puts (linebuffer);
+      /* gdb_stdout is buffered, and the caller must gdb_flush it at
+	 appropriate times.  Other streams are not so buffered.  */
+      if (file != gdb_stdout)
+	tui_refresh_cmd_win ();
     }
 }
 
@@ -239,6 +243,10 @@ tui_file_flush (struct ui_file *file)
     case astring:
       break;
     case afile:
+      /* gdb_stdout is buffered.  Other files are always flushed on
+	 every write.  */
+      if (file == gdb_stdout)
+	tui_refresh_cmd_win ();
       fflush (stream->ts_filestream);
       break;
     }
diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index 2b5a166..21b2a00 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -159,7 +159,10 @@ tui_putc (char c)
   tui_puts (buf);
 }
 
-/* Print the string in the curses command window.  */
+/* Print the string in the curses command window.
+   The output is buffered.  It is up to the caller to refresh the screen
+   if necessary.  */
+
 void
 tui_puts (const char *string)
 {
@@ -201,10 +204,6 @@ tui_puts (const char *string)
          TUI_CMD_WIN->detail.command_info.curch);
   TUI_CMD_WIN->detail.command_info.start_line
     = TUI_CMD_WIN->detail.command_info.cur_line;
-
-  /* We could defer the following.  */
-  wrefresh (w);
-  fflush (stdout);
 }
 
 /* Readline callback.
-- 
1.9.3