1760c37258
In the previous commit, we adjusted the callers of `fill_bitmap_tree()`
to pass in the bit position of the tree they wish to fill.
This commit makes use of that information at the call site to avoid
setting up a stack frame for fill_bitmap_tree() entirely whenever a
tree's bit position is already set.
Since this is such a hot path, the avoided cost of setting up and
tearing down stack frames for each noop'd call to `fill_bitmap_tree()`
is significant:
+--------------+-------------+-------------+-------------------+
| | HEAD^ | HEAD | Delta |
+--------------+-------------+-------------+-------------------+
| elapsed | 582.4 s | 562.8 s | -19.6 s (-3.4%) |
| cycles | 2,713.3 B | 2,621.3 B | -92.0 B (-3.4%) |
| instructions | 2,415.5 B | 2,348.9 B | -66.6 B (-2.8%) |
| CPI | 1.123 | 1.116 | -0.007 (-0.7%) |
+--------------+-------------+-------------+-------------------+
In the same repository as in the previous commit, our timings dropped
from ~582.4 seconds down to ~562.77 seconds.
While the cycles-per-instruction ratio is basically unchanged, we
execute significantly fewer instructions, and correspondingly fewer
cycles.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
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