Jeff King <peff <at> peff.net> writes: > > On Fri, Jul 15, 2016 at 02:46:28PM +0200, Ævar Arnfjörð Bjarmason wrote: > > > On Fri, Jul 15, 2016 at 2:18 PM, Jeff King <peff <at> peff.net> wrote: > > > Some features, like the index-helper, aren't quite so easy. One reason > > > is that its data needs to persist as a cache between multiple git > > > invocations. In general, I think it would be nice to solve that by > > > communicating via on-disk files, rather than a running daemon (just > > > because it has fewer moving parts). But that's only half of it for > > > index-helper. It needs to monitor inotify while git isn't running at > > > all; so it really _does_ need some kind of long-running daemon. > > > > This *may* have changed in the recent versions of the series, but I'm > > fairly sure and for what it's worth to this discussion, that's not > > what the index-helper does. It's there to keep the index file in > > memory instead of reading it from disk. > > > > It can *also* if you "git update-index --watchman" spawn a watchman > > daemon in the background, which is the thing that'll be doing the > > inotify calls and needs to stay persistent, the index-helper then > > communicates with the watchman daemon "what changed since X?" to > > compute a new index when requested. > > Ah, yeah, you're right. Sorry for the confusion; I haven't actually > followed the topic all that closely. > > -Peff >
That's very close. Index-helper currently keeps the index alive in memory and shares it with git.exe via shm so it does need to persist as a daemon. Otherwise, it will have to be run again and load the index from disk which pretty much defeats the purpose. Currently, it times out after a prescribed time of not being used and shuts down to just to free up the resources. The watchman daemon needs to _always_ be running so that it can monitor the working directory for changes and quickly provide the list of changed files and directories to git. This currently happens via index-helper but could be separated as the logic to use the data from watchman already exists in git. I have an RFC out that does exactly that.
