> On 15 Nov 2016, at 02:03, Eric Wong <e...@80x24.org> wrote: > > Lars Schneider <larsxschnei...@gmail.com> wrote: >> Hi, >> >> Git always performs a clean/smudge filter on files in sequential order. >> Sometimes a filter operation can take a noticeable amount of time. >> This blocks the entire Git process. > > I have the same problem in many places which aren't git :> > >> I would like to give a filter process the possibility to answer Git with >> "I got your request, I am processing it, ask me for the result later!". >> >> I see the following way to realize this: >> >> In unpack-trees.c:check_updates() [1] we loop through the cache >> entries and "ask me later" could be an acceptable return value of the >> checkout_entry() call. The loop could run until all entries returned >> success or error. >> >> The filter machinery is triggered in various other places in Git and >> all places that want to support "ask me later" would need to be patched >> accordingly. > > That all sounds reasonable. > > The filter itself would need to be aware of parallelism > if it lives for multiple objects, right?
Correct. This way Git doesn't need to deal with threading... >> Do you think this could be a viable approach? > > It'd probably require a bit of work, but yes, I think it's viable. > > We already do this with curl_multi requests for parallel > fetching from dumb HTTP servers, but that's driven by curl > internals operating with a select/poll loop. > > Perhaps the curl API could be a good example for doing this. Thanks for the pointer! >> Do you see a better way? > > Nope, I prefer non-blocking state machines to threads for > debuggability and determinism. Agreed! > Anyways, I'll plan on doing something similar (in Perl) with the > synchronous parts of public-inbox which relies on "cat-file --batch" > at some point... (my rotational disks are sloooooooow :<) That sounds interesting! What changes to you have in mind for "cat-file --batch"? We are thinking about performance improvements in that area, too. I would be happy to help reviewing your patches! Thanks a lot for your RFC feedback, Lars
