[Cocci] 0079-netdev-destructor.cocci very slow

Johannes Berg
2018-09-18T09:22:23Z

On Mon, 2018-09-17 at 23:55 +0200, Hauke Mehrtens wrote:
> The 0079-netdev-destructor.cocci spatch in backports is very slow for
> me. For bigger files I get a warning that it takes over to 15 seconds to
> apply it to just one file, for the complete backports tree it takes over
> an hour to apply.
>
> This is the patch:
> https://git.kernel.org/pub/scm/linux/kernel/git/backports/backports.git/tree/patches/0079-netdev-destructor.cocci
>
> When I remove the <-- --> in the first rule, it is applied in some
> seconds on the complete tree, so an speed improvement of about 100
> times, but it is not working correctly any more. ;-)
>
> Is this normal or how can I improve the spatch to be faster? I am using
> coccinelle 1.0.7 build with default configure arguments against the
> libraries from Debian stable.

We've had this discussion before :-)
I think we determined that it was normal.

> If this is normal I should probably try to reduce the number of files it
> tries to apply this against in gentree.py before spatch gets started.

spatch should already try that internally, but perhaps with some extra
knowledge we can do a better job ...

johannes