[yocto] Why did my build need to redo so many tasks?

[Martin Jansa]

On Thu, Feb 12, 2015 at 02:25:32PM -0700, Gary Thomas wrote:
> Yesterday, I built a large image using Poky/Yocto 870323cac1e
> Today I updated my Poky repo to 231d4a9d3
> 
> When I rebuilt the same image, bitbake kicked off more than
> 5200 tasks, building virtually every package from scratch.
> 
> How can I tell why this happened?  I don't have buildhistory
> enabled, but I do still have the tmp & sstate-cache trees
> from the process.  Is there enough info laying around that
> I can tell, e.g. why the GCC toolchain had to be rebuilt
> completely?
> 
> Am I correct in assuming that bitbake-whatchanged is really
> a Quija board and can only tell me [in advance] what will need
> to be done if my layers change?  When I ran it after the long
> build above, it didn't really tell me much :-(

I'm using
openembedded-core/scripts/sstate-diff-machines.sh
to create sstate signature snaphosts for interesting builds, then
when I'm surprised by number of re-executions, I create another snapshot
and compare them.

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa at gmail.com
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