bdiff: don't check border condition in loop
This is pretty much a copy of
d500ddae7494, just to a different loop.
The condition `p == plast` (`plast == a + len - 1`) was only true on
the final iteration of the loop. So it was wasteful to check for it
on every iteration. We decrease the iteration count by 1 and add an
explicit check for `p == plast` after the loop.
Again, we see modest wins.
From the mozilla-unified repository:
$ perfbdiff -m
3041e4d59df2
! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)
! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)
$ perfbdiff
0e9928989e9c --alldata --count 100
! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3)
! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3)
The 2nd example throws a total of ~3.3GB of data at bdiff. This
change increases the throughput from ~811 MB/s to ~924 MB/s.
Source bundle was generated with the following script:
# hg init
# echo a > a
# ln -s a l
# hg ci -Ama -d'0 0'
# mkdir b
# echo a > b/a
# chmod +x b/a
# hg ci -Amb -d'1 0'
$ hg init
$ hg -q pull "$TESTDIR/bundles/test-manifest.hg"
The next call is expected to return nothing:
$ hg manifest
$ hg co
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg manifest
a
b/a
l
$ hg files -vr .
2 a
2 x b/a (glob)
1 l l
$ hg files -r . -X b
a
l
$ hg manifest -v
644 a
755 * b/a
644 @ l
$ hg manifest --debug
b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644 a
b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 755 * b/a
047b75c6d7a3ef6a2243bd0e99f94f6ea6683597 644 @ l
$ hg manifest -r 0
a
l
$ hg manifest -r 1
a
b/a
l
$ hg manifest -r tip
a
b/a
l
$ hg manifest tip
a
b/a
l
$ hg manifest --all
a
b/a
l
The next two calls are expected to abort:
$ hg manifest -r 2
abort: unknown revision '2'!
[255]
$ hg manifest -r tip tip
abort: please specify just one revision
[255]