[PATCH] pci.id performance patch

[David Zeuthen]

On Thu, 2006-10-12 at 16:43 +0200, Danny Kukawka wrote:
> On Wednesday 11 October 2006 06:17, David Zeuthen wrote:
> > New commits:
> > diff-tree 5e33459557cf9d4680f894392a834b7752acd60a (from
> > e6b0bd21ae250d6d589e2584fd624b7bd2fa6835) Author: David Zeuthen
> > <davidz at redhat.com>
> > Date:   Wed Oct 11 00:17:34 2006 -0400
> >
> >     use mmap to access pci.ids and usb.ids
> >
> >     Goodbye 580KB of writable memory! :-)
> 
> I would propose to undo the change for pci.ids. We think the change from 
> writable memory to readonly memory doesn't bring better performance of HAL. 
> If we use writable memory we can optimize the process of search in the file.

This doesn't makes sense to me at all. Have you done any profiling to
actually verify that searching in pci.ids is a problem? If so, can you
share that? 

Saving 580kb of memory is _significant_. Making search within a function
50% faster doesn't really tell me anything, need profiles a'la the
sysprof stuff I was posting the other day.

Anyway, if you still think we need to speed it up the approach would be
this

 1. If cache file exist, compare mtime of cache file and pci.ids
 2. if pci.ids is older goto 5.
 3. Create binary optimized search structures from pci.ids
 4. Save those to a cache file file
 5. mmap the cache file
 6. setup inotify-ish stuff to track file changes and goto 1. on changes
 7. profit

That's what I'm planning to do for .fdi files anyway. Right now the fdi
rules files are "only" 80kb in memory (compared to 164k on disk) but
that is expected to grow a lot when we get battery recall data and
suspend quirks into HAL. Using mmap for that will be significant at
least long term.

> I attached a (slightly reworked) patch from Ihno Krumreich against git HEAD, 
> which we already use on SUSE since 0.5.6

It would be nice if you could send stuff like this upstream sooner.

    David