[coreboot] CBFS searches in Coreboot and SeaBIOS

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sat Sep 26 11:24:45 CEST 2009

On 26.09.2009 07:16, ron minnich wrote:
> On Fri, Sep 25, 2009 at 5:41 PM, Carl-Daniel Hailfinger
> <c-d.hailfinger.devel.2006 at gmx.net> wrote:
>> Given that ages ago my proposal to add caching for LAR entries was
>> rejected (and I don't think positions have changed since then), LAR/CBFS
>> walking will stay somewhat expensive.
> We have about 4 entries in the typical CBFS. I just don't see how the
> price of walking it can be a major item. It used to be until I created
> the "giant empty space" file. Now, walking a whole LAR can be done in
> short order. I'm happy to time it but I bet uncached it's still far
> less than one millisecond.
> We should always cache ROM and, if we are not, then, we should.
> I guess I am not sure this is a huge problem.

It is apparently enough of a problem to be noticed by Myles.

Myles, do you have any timing measurements we could use to assess the
impact for the non-verbose case? I know that serial printing slows
everything down to a crawl, but if the CBFS code emits no messages at
all, how long does it take to walk the entire ROM (unsuccessful walk)?



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