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Create a correctly-sized demangled names hashtable

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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
This commit is contained in:
Christian Biesinger 2019-11-18 16:37:31 -06:00
parent 85e7588dc4
commit f8bab2d61d
2 changed files with 18 additions and 2 deletions
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6
gdb/ChangeLog
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@ -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.

14
gdb/symtab.c
View File

@ -770,10 +770,20 @@ create_demangled_names_hash (struct objfile_per_bfd_storage *per_bfd)
/* 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));
}