Restore the data block size to 62.

The former block size traded away good fit within cache lines in
order to gain faster division in deque_item().  However, compilers
are getting smarter and can now replace the slow division operation
with a fast integer multiply and right shift.  Accordingly, it makes
sense to go back to a size that lets blocks neatly fill entire
cache-lines.

GCC-4.8 and CLANG 4.0 both compute "x // 62" with something
roughly equivalent to "x * 9520900167075897609 >> 69".
This commit is contained in:
Raymond Hettinger 2013-07-28 02:39:49 -07:00
parent 1f1d0a57fa
commit 77578204d6
2 changed files with 7 additions and 4 deletions

View file

@ -536,7 +536,7 @@ class TestBasic(unittest.TestCase):
@support.cpython_only
def test_sizeof(self):
BLOCKLEN = 64
BLOCKLEN = 62
basesize = support.calcobjsize('2P4nlP')
blocksize = struct.calcsize('2P%dP' % BLOCKLEN)
self.assertEqual(object.__sizeof__(deque()), basesize)