Re: [PATCH 00/23] [RFC] Builtin FSMonitor Feature

On 4/20/21 11:27 AM, Johannes Schindelin wrote:

Hi Junio,

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This RFC version includes support for Windows and MacOS file system events.
A Linux version will be submitted in a later patch series.

I guess this is another reason why this patch series did not see many
reviews: the lack of a Linux backend. And I fear that the statement "A
Linux version will be submitted in a later patch series" is a bit strong,
given that my original implementation of that backend does not really do
its job well: it uses `inotify` and therefore requires one handle _per
directory_, which in turn drains the number of file handles rather quickly
when your worktree has many directories. Meaning: It fails todoes not work in the
massive worktrees for which it was intended.

Now, I heard rumors that there is a saner way to monitor directory trees
in recent Linux kernel versions (Jeff, can you fill in where I am
blanking?) and it might be a good idea to solicit volunteers to tackle
this backend, so that the Linux-leaning crowd on this here mailing list
is interested a bit more?

Yes, I removed the early inotify-based version because the kernel limits
the number of inotify handles to 8k (at least on my Mint box) and that
is a global limit -- shared by any process wanting to use inotify.
The first monorepo that I tried it on had 120K directories in my
sparse checkout...

I'm told there is a newer "fanotify" facility available in newer
Linux kernels that behaves more like Windows and MacOS and handles
subdirectories.  I intend to jump into that shortly (unless someone
is already familiar with fanotify and and wants to try it).

Jeff