about when poky check sstate_cache #yocto


I read the codes about sstate_cache. Let me briefly talk about how it work . I am not sure if it is right.
Example,we have setscene tasks A_setsscene, B_setcene.
and Task C ,D are not setscene task.
After we bitbake something, runqueue started,and it check A , B to see if the sstate_caache exists and if exist, the poky does unpacking the cache and then ,ordinary build process starts and it will skip A and B.
So checking the existence and validation of sstate_cache is before ordinary build process instead of right before execcuting A and B(for example, we have a dependency tree, A,depend on X ,checking is before X instead of between X and A)
that's the result of my reading codes. And i did a small experienment that, in the middle of a clean bitbake project, i copiedĀ  all sstae_caches to the sstate_cache directory and it seemed the bitbake skips no task and unpacking did not happen.

Finally, i have a question. Can we move the checking and unpacking to, like the example above, right before executing A ,between X and A.
it means a lot to me. Cause the sharing of sstate_cache may be helpful to a more efficent parallel make(instead of just parallel make gcc jobs)

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