Change TT/TC hashing data structure (decreases memory by 50MB for memcheck 32bits)
This patch changes the way the transtab entries hash table is done.
Currently, the hash table is an open hash table considered full at 65%.
This means that in average, 1 entry on 3 is unused.
(all the hash table memory will be 'active' for big applications,
as the active entries are normally reasonably distributed over the hash table).
The size of a transtab entry is significant (about 150 Bytes).
To avoid having 35% of the entries unused, the translation table
is split in 2:
An hash table, that will contain an index pointing at the transtab entries.
With this technique, we are adding a small hash table,
but we spare 35% of the translation table.
Performance measurements have shown no degradation,
and some platforms have better performance. Not too clear why,
probably this helps platforms with small caches ?).
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15023 a5019735-40e9-0310-863c-91ae7b9d1cf9
1 file changed