On Sat, Apr 25, 2020 at 7:07 PM Nikolaus Rath <Nikolaus@xxxxxxxx> wrote:
>
> Hello,
>
> For debugging purposes, I would like to get information about read
> requests for FUSE filesystems that are answered from the page cache
> (i.e., that never make it to the FUSE userspace daemon).
>
> What would be the easiest way to accomplish that?
>
> For now I'd be happy with seeing regular reads and knowing when an
> application uses mmap (so that I know that I might be missing reads).
>
>
> Not having done any real kernel-level work, I would start by looking
> into using some tracing framework to hook into the relevant kernel
> function. However, I thought I'd ask here first to make sure that I'm
> not heading into the completely wrong direction.
Bpftrace is a nice high level tracing tool.
E.g.
sudo bpftrace -e 'kretprobe:fuse_file_read_iter { printf ("fuse
read: %d\n", retval); }'
Thanks,
Miklos
