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 t
cd t
hg branches
echo foo > a
hg add a
hg ci -m "initial" -d "1000000 0"
hg branch foo
hg branch
hg ci -m "add branch name" -d "1000000 0"
hg branch bar
hg ci -m "change branch name" -d "1000000 0"
echo % branch shadowing
hg branch default
hg branch -f default
hg ci -m "clear branch name" -d "1000000 0"
hg co foo
hg branch
echo bleah > a
hg ci -m "modify a branch" -d "1000000 0"
hg merge
hg branch
hg ci -m "merge" -d "1000000 0"
hg log
hg branches
hg branches -q
echo % test for invalid branch cache
hg rollback
cp .hg/branch.cache .hg/bc-invalid
hg log -r foo
cp .hg/bc-invalid .hg/branch.cache
hg --debug log -r foo
rm .hg/branch.cache
echo corrupted > .hg/branch.cache
hg log -qr foo
cat .hg/branch.cache
echo % update with no arguments: tipmost revision of the current branch
hg up -q -C 0
hg up -q
hg id
hg up -q 1
hg up -q
hg id
hg branch foobar
hg up
echo % fastforward merge
hg branch ff
echo ff > ff
hg ci -Am'fast forward' -d '1000000 0'
hg up foo
hg merge ff
hg branch
hg commit -m'Merge ff into foo' -d '1000000 0'
hg parents
hg manifest
exit 0