Re: [RFA 1/2] Speed up dict_hash

[Pedro Alves <palves@redhat.com>]

On 11/08/2017 06:44 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> 
>>> For "gdb -nx -readnow -batch gdb", this improves the time from ~9.8s
>>> before to ~8.5s afterward.
> 
> Pedro> Nice!
> 
> I rebuilt today and the baseline times were higher -- now it starts at
> ~14.1s for an unmodified gdb, down to ~12.2 with my patch.  I'm not sure
> if this is due to some other patch, or if the additional time is because
> I configured differently (I enabled guile, python, and all targets in
> this most recent build).  If so, 4 seconds (comparing to the ~10 seconds
> last time around) seems awfully expensive for those features...

I'm seeing a lot of time (24%!) spent in gettext, via complaints...
perf shows:

-   86.23%     0.00%  gdb      gdb                     [.] gdb_main
   - gdb_main
      - 85.60% catch_command_errors
           symbol_file_add_main_adapter
           symbol_file_add_main
           symbol_file_add_main_1
           symbol_file_add
         - symbol_file_add_with_addrs
            - 84.31% dw2_expand_all_symtabs
               - dw2_instantiate_symtab
                  - 83.79% dw2_do_instantiate_symtab
                     - 70.85% process_die
                        - 41.11% dwarf_decode_macros
                           - 41.09% dwarf_decode_macro_bytes
                              - 39.74% dwarf_decode_macro_bytes
                                 + 24.75% __dcigettext
                                 + 7.37% macro_define_object_internal
                                 + 3.16% macro_define_function
                                   0.77% splay_tree_insert
                                 + 0.76% savestring
                                 + 0.58% free
                                   0.53% read_indirect_string_at_offset_from
                                0.54% macro_define_object_internal
                                0.51% macro_start_file
                        + 25.57% process_die
                        + 4.07% dwarf_decode_lines
                     + 4.28% compute_delayed_physnames
                     + 3.85% end_symtab_from_static_block
                     + 3.38% load_cu
                     + 1.29% end_symtab_get_static_block
                  + 0.52% do_my_cleanups
            + 1.29% read_symbols
      + 0.54% gdb_init

Maybe you were building with --disable-intl before?

The problem is that we're computing the arguments to
pass to complaint, including passing the format strings
through gettext, even when complaints are disabled...  

The patch below, improves "gdb -nx -readnow -batch gdb"
from ~11.s to ~7.8s, for me (gcc 5.3.1, -O2, x86_64).

From c171f5097e05fa25553d92b9f9d14bf46207edc2 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Wed, 8 Nov 2017 21:03:15 +0000
Subject: [PATCH] complaints

---
 gdb/complaints.c |  4 ++--
 gdb/complaints.h | 17 ++++++++++++++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/gdb/complaints.c b/gdb/complaints.c
index 58b6b7b..22a5f69 100644
--- a/gdb/complaints.c
+++ b/gdb/complaints.c
@@ -148,7 +148,7 @@ find_complaint (struct complaints *complaints, const char *file,
    before we stop whining about it?  Default is no whining at all,
    since so many systems have ill-constructed symbol files.  */
 
-static int stop_whining = 0;
+int stop_whining = 0;
 
 /* Print a complaint, and link the complaint block into a chain for
    later handling.  */
@@ -236,7 +236,7 @@ vcomplaint (struct complaints **c, const char *file,
 }
 
 void
-complaint (struct complaints **complaints, const char *fmt, ...)
+complaint_1 (struct complaints **complaints, const char *fmt, ...)
 {
   va_list args;
 
diff --git a/gdb/complaints.h b/gdb/complaints.h
index 54c2b18..b6fa0e2 100644
--- a/gdb/complaints.h
+++ b/gdb/complaints.h
@@ -29,9 +29,20 @@ struct complaints;
 extern struct complaints *symfile_complaints;
 
 /* Register a complaint.  */
-extern void complaint (struct complaints **complaints,
-		       const char *fmt,
-		       ...) ATTRIBUTE_PRINTF (2, 3);
+extern void complaint_1 (struct complaints **complaints,
+			 const char *fmt,
+			 ...) ATTRIBUTE_PRINTF (2, 3);
+
+#define complaint(COMPLAINTS, FMT, ...)				\
+  do								\
+    {								\
+      extern int stop_whining;					\
+								\
+      if (stop_whining > 0)					\
+	complaint_1 (COMPLAINTS, FMT, ##__VA_ARGS__);		\
+    }								\
+  while (0)
+
 extern void internal_complaint (struct complaints **complaints,
 				const char *file, int line,
 				const char *fmt,
-- 
2.5.5