[yocto] Trying to re-use sstate.

[Scott Garman]

On 02/06/2012 07:08 AM, Chris Larson wrote:
> On Mon, Feb 6, 2012 at 12:53 AM, David Nyström<david.nystrom at enea.com>  wrote:
>> On 02/04/2012 05:51 AM, Scott Garman wrote:
>>>
>>> Hello,
>>>
>>> I'm trying to re-use the sstate from one build directory and move it to
>>> another. It's not working - bitbake is rebuilding *everything*.
>>>
>>> My hunch is the reason for this is because bblayers.conf must differ
>>> between the two build directories, because it uses full paths to the
>>> layer directories.
>>>
>>> By default, when you source oe-init-build-env for the first time, it
>>> generates a bblayers.conf file with full paths to the default layers,
>>> meta and meta-yocto.
>>>
>>> I thought the point of sstate was that I could copy it between build
>>> directories - or even different hosts - and save myself the effort of
>>> rebuilding everything if the remaining metadata was the same?
>>>
>>> Scott
>>>
>> We have the same issue,
>>
>> I tried to setup a buildbot to warm up sstate caches over night,
>> and let developers use this common sstate to speed up build times.
>> Epic fail, since paths usually are not consistent.
>> And it seems you can't even fake  an "identical path" with symlinks
>> either, bitbake detects the symlink and rebuilds everything.
>
>
> Afaik your BBLAYERS should not be in your signatures at all, unless
> something in the metadata is accessing it. For what it's worth, I
> reuse sstate every day, but don't use the poky/oe-core scripts
> (oe-init-build-env).

As a follow-up to this thread, I spent a bit of time today trying to 
reproduce/isolate the issue, and I could not do so. Changing the paths 
to layers correctly rebuilt from sstate, and adding an empty layer also 
didn't trigger a rebuild. So I'm not sure what I saw previously, but 
unfortunately my original example of this is no longer available for me 
to work with.

I apologize for causing any confusion, but it's still quite possible we 
have some issues - I'll definitely use bitbake-diffsig to dig deeper the 
next time I see it.

Scott

-- 
Scott Garman
Embedded Linux Engineer - Yocto Project
Intel Open Source Technology Center