Junio C Hamano wrote: > 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. Is the BSD kernel's inotify the same as the one on Linux? Must we design something that's generic enough from the start? More importantly, do you know of a platform-independent inotify implementation in C? A quick Googling turned up QFileSystemWatcher [1], a part of QT. [1]: http://qt-project.org/doc/qt-4.8/qfilesystemwatcher.html > - 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. UNIX domain sockets are also preferred because we'd never want to connect to a watch daemon over the network? Then the communication channel code also has to be generic enough. > - 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. Right. -- 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