On 7/24/2020 9:52 PM, Taylor Blau wrote: > On Fri, Jul 24, 2020 at 12:47:00PM -0700, Junio C Hamano wrote: >> Derrick Stolee <stolee@xxxxxxxxx> writes: >> >>> But you are discussing here how the _behavior_ can change when >>> --auto is specified. And specifically, "git gc --auto" really >>> meant "This is running after a foreground command, so only do >>> work if necessary and do it quickly to minimize blocking time." >>> >>> I'd be happy to replace "--auto" with "--quick" in the >>> maintenance builtin. >>> >>> This opens up some extra design space for how the individual >>> tasks perform depending on "--quick" being specified or not. >>> My intention was to create tasks that are already in "quick" >>> mode: >>> >>> * loose-objects have a maximum batch size. >>> * incremental-repack is capped in size. >>> * commit-graph uses the --split option. >>> >>> But this "quick" distinction might be important for some of >>> the tasks we intend to extract from the gc builtin. >> >> Yup. To be honest, I came to this topic from a completely different >> direction. The field name "auto" alone (and no other field name) >> had to have an extra cruft (i.e. "_flag") attached to it, which is >> understandable but ugly. Then I started thinking if 'auto(matic)' >> is really the right word to describe what we want out of the option, >> and came to the realization that there may be better words. > > I wonder what the quick and slow paths are here. For the commit-graph > code, what you wrote here seems to match what I'd expect with passing > '--auto' in the sense of running 'git gc'. That is, I'm leaving it up to > the commit-graph machinery's idea of the normal '--split' rules to > figure out when to roll up layers of a commit-graph, as opposed to > creating a new layer and extending the chain. I had intended all of my new tasks to be the "quick" version of their operations. The "slow" version would abandon hope of doing a small amount of work to create the best possible world for the repository. This would include: * The commit-graph would collapse all layers into one file. * The multi-pack-index repack would rewrite all object data into one pack-file. * The loose-objects task would not stop at a maximum number of loose objects (and would probably want to repack everything, anyway). I'm open to making this possibility more explicit by renaming "--auto" and just performing a translation to 'git gc --auto'. So, what should the name be? Here are a few options to consider: --quick --fast --limited --incremental -O[0|1|2...] (think GCC optimization flags, exposing granularity) --[non-]aggressive Regardless, this makes me rethink that the --[no-]maintenance option from PATCH 03/18 is better than --[no-]auto-maintenance, since we are really saying "run _some_ maintenance or _no_ maintenance" and the "how" of the maintenance is left intentionally vague. I've already made the change locally to add "auto-" so I'll wait for confirmation before reverting that change. > So, I think that makes sense if the caller gave '--auto'. But, I'm not > sure that it makes sense if they didn't, in which case I'd imagine > something quicker to happen. There, I'd expect something more like: > > 1. Run 'git commit-graph write --reachable --split=no-merge'. > 2. Run 'git commit-graph verify'. > 3. If 'git commit-graph verify' failed, drop the existing commit graph > and rebuild it with 'git commit-graph --reachable --split=replace'. > 4. Otherwise, do nothing. > > I'm biased, of course, but I think that that matches roughly what I'd > expect to happen in the fast/slow path. Granted, the steps to rebuild > the commit graph are going to be slow no matter what (depending on the > size of the repository), and so in that case maybe the commit-graph > should just be dropped. I'm not really sure what to do about that... I think this approach is the best we can do given the current behavior inside the commit-graph builtin. Perhaps in the future we could change the commit-graph builtin to include a "--verify" option so it could do the "git commit-graph verify --shallow" on the new layer before committing the new commit-graph-chain file and expiring old layers. That way, we would not need to delete and rewrite the whole thing when there is a problem writing the top layer. >>> Since the tasks are frequently running subcommands, returning >>> 0 for success and non-zero for error matches the error codes >>> returned by those subcommands. >> >> As long as these will _never_ be called from other helper functions >> but from the cmd_foo() top-level and their return values are only >> used directly as the top-level's return value, I do not mind too >> much. >> >> But whenever I am writing such a code, I find myself not brave >> enough to make such a bold promise (I saw other people call the >> helpers I wrote in unintended ways and had to adjust the semantics >> of them to accomodate the new callers too many times), so I'd rather >> see the caller do "return !!helper_fn()" to allow helper_fn() to be >> written more naturally (e.g. letting them return error(...)). I will try to be consistent here with the behavior: * 0 is success * 1 is failure Which is what I think you are implying by "return !!helper_fn()". Thanks, -Stolee
