[OE-core] Over-pruning the sstate cache

[Richard Purdie]

On Tue, 2016-04-12 at 19:51 +0100, Mike Crowe wrote:
> 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?

In theory the key part is the hash, all the other pieces are there just
to make human understandable filenames/layout (and would be encoded
into the hash in most cases). Whilst we could generate that info, I'm
not sure it would help much since the hashes should uniquely identify
the files?

Cheers,

Richard