Re: [RFC \ WISH] Add -o option to git-rev-list

["Marco Costalba" <mcostalba@gmail.com>]

On 12/11/06, Linus Torvalds <torvalds@osdl.org> wrote:
>
>
>
> However, you seem to continually ignore the thing I've asked you to do
> several times: try with a cold-cache situation.

Yes. I will test it. I was testing with warm cache also to my
curiosity about comparing pipes with temporary file reading as data
exchange facility. So I needed to avoid HD artifacts.

>
>
>   At that point, you'd actually do something that gitk can't do at all,
>   namely work well for the cold-cache not-very-packed large-repository
>   case. ]
>

Removing --topo-order from launch parameters is very simple, see from
gitstartup.cpp:

bool Git::startRevList(SCRef args, FileHistory* fh) {

	QString initCmd("git rev-list --header --boundary --parents ");
	if (!isMainHistory(fh)) {
		// fetch history from all branches so any revision in
		// main view that changes the file is always found
		SCRef allBranches = getAllRefSha(BRANCH).join(" ");
		initCmd.append("--remove-empty " + allBranches + " -- ");
	} else
		initCmd.append("--topo-order ");

	return startParseProc(initCmd + args, fh);
}

It is already removed from file history fetching because there the
history it's _almost_ linear and you gain the speed without noticing
the different graph layout. But for main view I fear that complicated
branch structures could became difficult to follow without
--topo-order. Perhaps an option in settings?

> To see this in practice (even with hot-caches), do something like the
> following on the full historic Linux archive:
>
>         time sh -c "git rev-list HEAD | head"
>         time sh -c "git rev-list --topo-order HEAD | head"
>
> where for me, the firstone takes 0.002s, and the second one takes 0.878s.
>

This is  the data:

$ pwd
/git/linux-2.6
bash-3.1$ time sh -c "git rev-list HEAD | head"
200d018eff4be3a1fb9823441cfcebb7de86a677
f0647a52974daccbe20990fb6341f07792445fe0
c25c79d80e02db1bd993426f979c5f1b42a0f132
9fd32cfbb602f3e5e898faa61d83c4a7897bd48a
ed99e2bc1dc5dc54eb5a019f4975562dbef20103
773ff78838ca3c07245e45c06235e0baaa5f710a
52ffe760ea9ec407292d093c3f06c1cda5187228
14b36af46a1d3652aff6734ea24816995dff8123
eb991b39385c7b04923d701764a34694ec54b53d
88032b322a38b37335c8cb2e3473a45c81d280eb
0.08user 0.02system 0:00.10elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+3631minor)pagefaults 0swaps

bash-3.1$  time sh -c "git rev-list --topo-order HEAD | head"
200d018eff4be3a1fb9823441cfcebb7de86a677
f0647a52974daccbe20990fb6341f07792445fe0
c25c79d80e02db1bd993426f979c5f1b42a0f132
9fd32cfbb602f3e5e898faa61d83c4a7897bd48a
ed99e2bc1dc5dc54eb5a019f4975562dbef20103
773ff78838ca3c07245e45c06235e0baaa5f710a
52ffe760ea9ec407292d093c3f06c1cda5187228
14b36af46a1d3652aff6734ea24816995dff8123
eb991b39385c7b04923d701764a34694ec54b53d
33ec32fae0e2c4433bfd1e74cbde6cb16604a719
2.84user 0.12system 0:03.05elapsed 97%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+12086minor)pagefaults 0swaps

Also the long awaited ;-)

$ time sh -c "git rev-list --header --boundary --parents --topo-order
HEAD | cat > /dev/null"
3.75user 0.55system 0:04.42elapsed 97%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+18822minor)pagefaults 0swaps

$ time sh -c "git rev-list --header --boundary --parents --topo-order
HEAD > /tmp/tmp.txt; cat /tmp/tmp.txt > /dev/null"
3.50user 0.30system 0:03.92elapsed 97%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+18800minor)pagefaults 0swaps