Junio C Hamano <gitster@xxxxxxxxx> writes: > I checked read-cache.c and preload-index.c code. To get the > discussion rolling, I think something like the outline below may be > a good starting point and a feasible weekend hack for somebody > competent: > > * At the beginning of preload_index(), instead of spawning the > worker thread and doing the lstat() check ourselves, we open a > socket to our daemon (see below) that watches this repository and > make a request for lstat update. The request will contain: > > - The SHA1 checksum of the index file we just read (to ensure > that we and our daemon share the same baseline to > communicate); and > > - the pathspec data. > > Our daemon, if it already has a fresh data available, will give > us a list of <path, lstat result>. Our main process runs a loop > that is equivalent to what preload_thread() runs but uses the > lstat() data we obtained from the daemon. If our daemon says it > does not have a fresh data (or somehow our daemon is dead), we do > the work ourselves. > > * Our daemon watches the index file and the working tree, and > waits for the above consumer. First it reads the index (and > remembers what it read), and whenever an inotify event comes, > does the lstat() and remembers the result. It never writes > to the index, and does not hold the index lock. Whenever the > index file changes, it needs to reload the index, and discard > lstat() data it already has for paths that are lost from the > updated index. I left the details unsaid in thee above because I thought it was fairly obvious from the nature of the "outline", but let me spend a few more lines to avoid confusion. - The way the daemon "watches" the changes to the working tree and the index may well be very platform dependent. I said "inotify" above, but the mechanism does not have to be inotify. - The channel the daemon and the client communicates would also be system dependent. UNIX domain socket in $GIT_DIR/ with a well-known name would be one possibility but it does not have to be the only option. - The data given from the daemon to the client does not have to include full lstat() information. They start from the same index info, and the only thing preload_index() wants to know is for which paths it should call ce_mark_uptodate(ce), so the answer given by our daemon can be a list of paths. -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html