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

Pedro Alves
2015-02-04T11:55:46Z

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