Re: [patch] Eliminate quadratic slow-down on number of solibs (part 2).

[Paul Pluzhnikov <ppluzhnikov@google.com>]

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On Fri, May 1, 2009 at 3:16 PM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote:

> This is the patch to eliminate repeated iteration over the same objfile
> looking for Objective-C methods, as Tom suggested here:
>  http://sourceware.org/ml/gdb-patches/2009-04/msg00551.html

Even after the two patches above, there is still some repeated
and unnecessary setting and resetting of the breakpoints as each
solib is added :-(

Attached is an alternative patch which subsumes the other two,
and kills additional 15% of wasted CPU time.

It feels like a hack, but I don't see how to achieve the same
result in a cleaner way :-(

Timing on my 2780-solib test (just running ldd on that takes 15s):

time gdb -ex 'break main' -ex run -ex kill -ex quit request_test

=== current CVS Head ===
real    11m16.762s
user    11m5.530s
sys     0m9.697s

=== with attached patch ===
real    2m43.595s
user    2m33.350s
sys     0m9.353s

Tested on Linux/x86_64 without regressions.

Comments?
--
Paul Pluzhnikov

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? foof.12580
Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.393
diff -u -p -u -r1.393 breakpoint.c
--- breakpoint.c	5 May 2009 13:24:48 -0000	1.393
+++ breakpoint.c	6 May 2009 00:46:59 -0000
@@ -72,6 +72,9 @@
 #define CATCH_PERMANENT ((void *) (uintptr_t) 0)
 #define CATCH_TEMPORARY ((void *) (uintptr_t) 1)
 
+/* If non-zero, breakpoin_re_set() is a no-op.  */
+int suppress_breakpoint_reset;
+
 /* Prototypes for local functions. */
 
 static void enable_delete_command (char *, int);
@@ -7723,6 +7726,9 @@ breakpoint_re_set (void)
   enum language save_language;
   int save_input_radix;
 
+  if (suppress_breakpoint_reset)
+    return;
+
   save_language = current_language->la_language;
   save_input_radix = input_radix;
   ALL_BREAKPOINTS_SAFE (b, temp)
Index: breakpoint.h
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.h,v
retrieving revision 1.90
diff -u -p -u -r1.90 breakpoint.h
--- breakpoint.h	31 Mar 2009 16:44:17 -0000	1.90
+++ breakpoint.h	6 May 2009 00:46:59 -0000
@@ -669,6 +669,8 @@ enum breakpoint_here
     permanent_breakpoint_here
   };
 \f
+/* If non-zero, breakpoin_re_set() is a no-op.  */
+extern int suppress_breakpoint_reset;
 
 /* Prototypes for breakpoint-related functions.  */
 
Index: solib.c
===================================================================
RCS file: /cvs/src/src/gdb/solib.c,v
retrieving revision 1.115
diff -u -p -u -r1.115 solib.c
--- solib.c	9 Mar 2009 22:38:37 -0000	1.115
+++ solib.c	6 May 2009 00:46:59 -0000
@@ -738,6 +738,9 @@ solib_add (char *pattern, int from_tty, 
     int any_matches = 0;
     int loaded_any_symbols = 0;
 
+    /* Delay resetting breakpoints until after we added all solibs.  */
+    suppress_breakpoint_reset += 1;
+
     for (gdb = so_list_head; gdb; gdb = gdb->next)
       if (! pattern || re_exec (gdb->so_name))
 	{
@@ -754,6 +757,10 @@ solib_add (char *pattern, int from_tty, 
 	    loaded_any_symbols = 1;
 	}
 
+    suppress_breakpoint_reset -= 1;
+    if (loaded_any_symbols)
+      breakpoint_re_set ();
+
     if (from_tty && pattern && ! any_matches)
       printf_unfiltered
 	("No loaded shared libraries match the pattern `%s'.\n", pattern);