[pushed] Create a correctly-sized demangled names hashtable

Sourceware to Gerrit sync (Code Review)
2019-11-22T17:44:17Z

The original change was created by Christian Biesinger.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/686
......................................................................

Create a correctly-sized demangled names hashtable

If we have a minsym count, we know the demangled names hashtable will
be at least that big. So use that count to size it, so we don't
have to resize/rehash it as much.

This is a 6% improvement in minsym loading time.

2019-11-22 Christian Biesinger <cbiesinger@google.com>

* symtab.c (create_demangled_names_hash): Use per_bfd->
minimal_symbol_count for computing the initial size, if greater
than our default size.

Change-Id: I1f074d38e1d90af58705ec852f90c84cc034cd2e
---
M gdb/ChangeLog
M gdb/symtab.c
2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 93258c3..838262e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-11-22 Christian Biesinger <cbiesinger@google.com>
+
+ * symtab.c (create_demangled_names_hash): Use per_bfd->
+ minimal_symbol_count for computing the initial size, if greater
+ than our default size.
+
2019-11-22 Tom de Vries <tdevries@suse.de>

* contrib/words.sh: Improve words extraction.
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 0064800..6affdef 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -770,10 +770,20 @@
/* Choose 256 as the starting size of the hash table, somewhat arbitrarily.
The hash table code will round this up to the next prime number.
Choosing a much larger table size wastes memory, and saves only about
- 1% in symbol reading. */
+ 1% in symbol reading. However, if the minsym count is already
+ initialized (e.g. because symbol name setting was deferred to
+ a background thread) we can initialize the hashtable with a count
+ based on that, because we will almost certainly have at least that
+ many entries. If we have a nonzero number but less than 256,
+ we still stay with 256 to have some space for psymbols, etc. */
+
+ /* htab will expand the table when it is 3/4th full, so we account for that
+ here. +2 to round up. */
+ int minsym_based_count = (per_bfd->minimal_symbol_count + 2) / 3 * 4;
+ int count = std::max (per_bfd->minimal_symbol_count, minsym_based_count);

per_bfd->demangled_names_hash.reset (htab_create_alloc
- (256, hash_demangled_name_entry, eq_demangled_name_entry,
+ (count, hash_demangled_name_entry, eq_demangled_name_entry,
free_demangled_name_entry, xcalloc, xfree));
}

--
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I1f074d38e1d90af58705ec852f90c84cc034cd2e
Gerrit-Change-Number: 686
Gerrit-PatchSet: 3
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Kevin Buettner <kevinb@redhat.com>
Gerrit-CC: Simon Marchi <simon.marchi@polymtl.ca>
Gerrit-MessageType: newpatchset