[bitbake-devel] [PATCH 0/2] Variable tracking: Cleaned up and rebased.

[Peter Seebach]

On Wed, 16 Jan 2013 17:54:58 +0000
Richard Purdie <richard.purdie at linuxfoundation.org> wrote:

> I *really* want to take these, however I did want to check
> performance:

Oh, good thought.

> $ time bitbake core-image-sato -e
> real	0m8.034s
> $ time bitbake -p
> real	0m12.220s
> user	3m3.887s
 
> After:
 
> $ time bitbake core-image-sato -e
> real	0m50.267s
> $ time bitbake -p
> real	0m14.607s
> user	3m55.179s

Hmm. That doesn't totally surprise me.
 
> The 50s seems a touch excessive and it looks like a 20% parsing hit
> even when unused :(. Note the overall parsing times on this machine
> are fast as its running 24 in parallel. I'm going to try and figure
> out what is going on tomorrow as I've fixed a lot of this kind of
> thing in the past but wanted to mention it...

The 50s seems... not entirely surprsing. I don't know that much about
how Python does stuff, but in practice we end up with a LOT of deep
copies of structures floating around because there are a ton of data
copies; without these, finalize information gets duplicated and things
go pretty wrong.

My intuition is that the stack backtrace thing is probably expensive,
and might be noticably reduced by manually passing in the
likely-missing values in cases where we know what they are, so it's
less likely that any backtracing has to happen.

-s
-- 
Listen, get this.  Nobody with a good compiler needs to be justified.