Improving the offline updates user experience

[Miroslav Suchý]

On 09/15/2014 10:06 AM, Richard W.M. Jones wrote:
> It wasn't clear to me how tracer works for non-C programs.

https://github.com/FrostyX/tracer/commit/4abfc4ecbc6d1d4cd89b7162e1ba3f63088db3ff

Which basicaly checkout output of `ps` and if there is e.g. python as executable, it will check for arguments and use those.
But I agree that interpreted languages are problem, because they open the file, read it and close the handler.
So there are no footsteps to track.

> However there was some Red Hat only discussion recently about how to
> do this for Python programs, with minimal overhead.  Below I'm just
> reproducing a technique (untested) that I think will work for Python.
>
> It requires a small patch to the Python interpreter, and a similar
> patch to any other language interpreters (eg. Perl, Ruby).
>
> Rich.
>
> -------
> For each module (*.py or *.pyc) that it imports, have it mmap the
> first page of that file into its memory.
>
> The mmap would be PROT_NONE because it's not actually used, and the
> associated file descriptor should be closed.
>
> This will appear in /proc/PID/maps, with a "(deleted)" flag if the
> underlying file gets deleted (and hence the process needs restarting).
>
> The cost should be almost nothing:
>
>   - 4K of virtual memory, no real memory
>   - an extra mmap syscall on import
>   - an extra segment in the kernel's VM AVL
> -------

Very nice.
Is there some bugzilla RFE report for this? Or should I file it?


-- 
Miroslav Suchy, RHCE, RHCDS
Red Hat, Senior Software Engineer, #brno, #devexp, #fedora-buildsys