view tests/test-empty-file @ 5339:058e93c3d07d

I have spotted the biggest bottleneck in "bdiff.c". Actually it was
pretty easy to find after I recompiled the python interpreter and
mercurial for profiling.

In "bdiff.c" function "equatelines" allocates the minimum hash table
size, which can lead to tons of collisions. I introduced an
"overcommit" factor of 16, this is, I allocate 16 times more memory
than the minimum value. Overcommiting 128 times does not improve the
performance over the 16-times case.

#!/bin/sh

hg init a
cd a
touch empty1
hg add empty1
hg commit -m 'add empty1' -d '1000000 0'

touch empty2
hg add empty2
hg commit -m 'add empty2' -d '1000000 0'

hg up -C 0
touch empty3
hg add empty3
hg commit -m 'add empty3' -d '1000000 0'

hg heads

hg merge 1
# before changeset 05257fd28591, we didn't notice the
# empty file that came from rev 1.
hg status
hg commit -m merge -d '1000000 0'
hg manifest --debug tip