[PATCH] Speed up modprobe and MAKEDEV

[Jon Masters]

On Mon, 2008-10-13 at 10:24 -0400, Jon Masters wrote:
> On Mon, 2008-10-13 at 16:10 +0200, Jakub Jelinek wrote:
> 
> > FYI, here is a tiny incremental fix for the patch I've posted earlier
> > - Mandriva folks reported that with my patch depmod was upset when run
> > on a tree with no modules at all.
> 
> :) Though if we ever manage to "demodularize for the win" to that point,
> well, it'll be quite exciting!
> 
> I'm testing your 3.4.1 patch against today's 3.5 tree and will followup
> with some results. Whichever performs best, I'll keep. Sorry I didn't
> sort this out sooner, but it's time to move forward and get this sorted
> out - and there are more trivial fixes I've got in mind. As of today's
> rawhide there are also no longer any Fedora-specific patches left.

In one test, I ran modprobe about 8000 times on a desktop.

older modprobe:       190.03user 25.19system 3:55.54elapsed 91%CPU
upstream modprobe:      8.65user 19.69system 0:31.08elapsed 91%CPU
Jakob's modprobe:       6.71user 18.05system 0:27.01elapsed 91%CPU

The latter two vie a little between each other, but basically are
comparable. So for now, I'll keep upstream as it is and do some more
testing/write some scripts. Then I'll do some migration to unlocked
non-threaded functions and pull in other parts of Jakob's patch. I'm
thinking there are actually other places to focus on now - more
profiling will be called for and I'll push some more updates.

Older modprobe is 3.4.1, upstream is 3.5 (radix trie implementation),
Jakob's patch uses a hashtable/bucket mechanism.

Jon.