[review,v2] Create a correctly-sized demangled names hashtable
Commit Message
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/686
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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.
2019-11-18 Christian Biesinger <cbiesinger@google.com>
* symtab.c (create_demangled_names_hash): Use per_bfd->
minimal_symbol_count as the initial size, if greater than
our default size.
Change-Id: I1f074d38e1d90af58705ec852f90c84cc034cd2e
---
M gdb/symtab.c
1 file changed, 12 insertions(+), 2 deletions(-)
@@ -769,10 +769,20 @@
/* 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));
}