[OE-core] Over-pruning the sstate cache

[Mike Crowe]

On Tuesday 29 March 2016 at 15:11:10 +0100, Richard Purdie wrote:
> On Tue, 2016-03-29 at 13:56 +0100, Mike Crowe wrote:
> > 80b3974081c4a8c604e23982a6db8fb32c616058 implies that at least some
> > people
> > are pruning the sstate cache based on file access time.
> > 
> > Is there a recommended way to ensure that all the sstate cache files
> > are
> > touched, even those that are not actually required to build the image
> > currently due to task optimisation?
> > 
> > Does anyone have any better ideas?
> 
> generate the "locked-sigs" inc file (bitbake XXX -S none) and then with
> a script touch all the objects listed in that file?

I'm most of the way through writing a script to do this. I've discovered
that the sstate filenames contain bits that aren't in the locked-sigs file
such as ${PV}, ${PR}, ${TARGET_VENDOR}, ${TARGET_OS}, ${SSTATE_VERSION}.
The hash is the important bit for identifying the file uniquely so these
bits can either be hard coded or wildcarded as appropriate.

There's also the need to apply native OS name prefix for native packages.

Is there a a way of getting hold of those bits so I can avoid the
wildcards?

Thanks.

Mike.