[OE-core] uninative and recipe parsing

[Richard Purdie]

On Mon, 2018-03-12 at 11:04 +0000, Cuero Bugot wrote:
> Hi all,
> 
> When you add several layers, recipe parsing can take a (very) long
> time. In our case it takes more than a couple minutes [1].
> Fortunately it is supposed to happens once, except when you use
> uninative (poky's default) where it happens twice (the two first
> times you build).
> I think this is not an intentional behavior so I dug it a little bit
> and here is what I found:
> 
> When inheriting meta/classes/uninative.bbclass, it registers 2
> functions on build events: one to fetch the uninative tarball (at
> bb.event.BuildStarted) and the other one to set variables in the
> datastore (at bb.event.ConfigParsed).
> The function that set the variables [2] to the datastore first check
> that the uninative blob is in the build tree, so even though it is
> supposed to happen at recipe parsing, the variable are only really
> set when the build really start (bb.event.BuildStarted), after the
> recipes have been parsed!
> 
> So I think there is bug in the current behavior as:
> 	* Either the uninative variables are not important for the
> recipe parsing, and then they should be added in
> BB_HASHCONFIG_WHITELIST
> 	* Or the variables should matter for the recipe parsing so they
> should be set before the parsing and not in between parsing and
> build.
> 
> I assumed the later, so a simple fix is to register the two functions
> on the same event: bb.event.ConfigParsed.
> 
> Note: We are currently using pyro, but I checked that the master
> branch should exhibit the same behavior (same code).
> 
> [1]: it matters to us as we are doing Continuous Integration and do
> clean builds (with sstate cache) on every pull requests and master
> branch commits. The automatic test full cycle take about 20 minutes.
> We launch 2 bitbake commands during that process. Parsing recipe take
> about 2-4 minutes, which is significant enough when trying to reduce
> the waiting and parallel builds/tests.
> [2]: the uninative changed variables are: NATIVELSBSTRING,
> SSTATEPOSTUNPACKFUNCS
> 
> Proposed patch:
> 
> diff --git a/meta/classes/uninative.bbclass
> b/meta/classes/uninative.bbclass
> index a410647..5713bb8 100644
> --- a/meta/classes/uninative.bbclass
> +++ b/meta/classes/uninative.bbclass
> @@ -9,7 +9,7 @@ UNINATIVE_TARBALL ?= "${BUILD_ARCH}-nativesdk-
> libc.tar.bz2"
>  UNINATIVE_DLDIR ?= "${DL_DIR}/uninative/"
>  
>  addhandler uninative_event_fetchloader
> -uninative_event_fetchloader[eventmask] = "bb.event.BuildStarted"
> +uninative_event_fetchloader[eventmask] = "bb.event.ConfigParsed"
>  
>  addhandler uninative_event_enable
>  uninative_event_enable[eventmask] = "bb.event.ConfigParsed"

I have kind of noticed this and agree its something we should fix.
Thanks for digging into it. I think a long time ago we tried the above
change and it does cause a problem, perhaps fetching during parsing
which is bad.

Have you been able to figure out what changes in the data store for the
cache to be invalidated? I think whitelisting something may be the best
solution, or perhaps only activating certain changes in the build code
paths after parsing in all cases.

Cheers,

Richard