[OE-core] sstate-cache contains many seemingly useless siginfo files

[Mike Crowe]

On Monday 01 February 2016 at 17:52:31 +0000, Richard Purdie wrote:
> On Mon, 2016-02-01 at 16:59 +0000, Mike Crowe wrote:
> > Our sstate-cache cleanup script was written long before
> > 80b3974081c4a8c604e23982a6db8fb32c616058, so it only pruned siginfo
> > files
> > if the corresponding tgz file had not been accessed recently.
> > 
> > This worked well until siginfo files started being written for every
> > task -
> > even those that didn't also generate a tgz file such as unpack,
> > configure
> > and compile.
> > 
> > I've just cleared up over two million siginfo files from our sstate
> > -cache!
> > 
> > This exercise has left me wondering why these siginfo files are being
> > written to the sstate-cache in the first place.
> > 80b3974081c4a8c604e23982a6db8fb32c616058 suggests that they aren't
> > being
> > used by anyone.
> 
> These are used by things like "bitbake -S printdiff" in order to debug
> why things are being rebuilt. Without them, there are gaps in the
> dependency chains and the tools can't figure out how things changed.
> 
> So they're not used by main builds but are useful for debug.

It sounds like keeping them around would be useful, but since they aren't
touched during a normal build they would be expired from the sstate-cache
while they are still current.

But, perhaps running "bitbake -S printdiff" periodically would be
sufficient to ensure that they are accessed and won't expire early. I'll
try doing that.

Thanks.

Mike.