Re: [Buildroot] [PATCH 2/3] support/tests: allow top-level parallel builds

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Thomas, All,

On 2022-12-27 21:45 +0100, Thomas Petazzoni via buildroot spake thusly:
> On Sat, 24 Dec 2022 10:18:12 +0100
> "Yann E. MORIN" <yann.morin.1998@free.fr> wrote:
> > Running tests with top-level parallel builds can speed up running some
> > tests, expecially those that have a lot of packages like the systemd
> > init tests.
> > 
> > Trigger TLPB when the configuration enables per-package directories.
> > 
> > Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
> > Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> 
> I certainly support the idea of running some tests with TLPB. However,
> this implementation makes a confusion between two different settings:
> 
> - The existing BRConfigTest.jlevel, which is set by run-tests -j, and
>   used to define BR2_JLEVEL in the Buildroot configuration of each test
>   case. This determines the number of parallel jobs used to build each
>   independent package.
> 
> - Your new work, which uses "make -j" to do TLPB... but relies on the
>   same above value, even though it's a completely different setting.
> 
> Is this expected?

Yes, this is the intended behaviour, which I was explicitly seeking.

So, if one runs with PPD and TLPB (outside the run-time infra), one
would do something like:

    $ make -jN

This spawns a top-level make process that is parallel. In turn, in
rules, when we call $(MAKE), this is the magic that tells make that
it is recursive, but that it should use the jobserver from the calling
process.

So, in this case, the BR2_JLEVEL is unused by whatever uses the make
jobserver; only the number of jobs in the top-level jobserver is
meaningful, i.e. whatever we pass as -jN.

The exception, of course, is whatever uses BR2_JLEVEL but does not talk
to the jobserver, but this is mostly a few packages (scons, waf et al.).
Even ninja packages do talk to the top-level jobserver, now that we use
the ninja fork that knows to talk to it.

So, yes, using top-level -jN with the same value as BR2_JLEVEL is
exactly what I intended to do.

Unless I totally missed something...

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 561 099 427 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot