linux-kernel - Re: [PATCH] kbuild: add debug package to pacman PKGBUILD

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Message-ID: <CAK7LNARAHBS9OR5R2EzwKQQonWmF=H1a-C6xG9K2GAWJ8dk43w@mail.gmail.com>
Date: Sat, 3 Aug 2024 23:40:41 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Nathan Chancellor <nathan@...nel.org>, Jose Fernandez <jose.fernandez@...ux.dev>, 
	Christian Heusel <christian@...sel.eu>, Nicolas Schier <nicolas@...sle.eu>, 
	Peter Jung <ptr1337@...hyos.org>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kbuild: add debug package to pacman PKGBUILD

On Fri, Aug 2, 2024 at 3:54 AM Thomas Weißschuh <linux@...ssschuh.net> wrote:
>
> On 2024-08-01 11:36:37+0000, Nathan Chancellor wrote:
> > Hi Jose,
> >
> > On Thu, Aug 01, 2024 at 07:29:40AM -0600, Jose Fernandez wrote:
> > > Add a new -debug package to the pacman PKGBUILD that will contain the
> > > vmlinux image for debugging purposes. This package depends on the
> > > -headers package and will be installed in /usr/src/debug/${pkgbase}.
> > >
> > > The vmlinux image is needed to debug core dumps with tools like crash.
> > >
> > > Signed-off-by: Jose Fernandez <jose.fernandez@...ux.dev>
> > > Reviewed-by: Peter Jung <ptr1337@...hyos.org>
> >
> > This appears to add a non-trivial amount of time to the build when benchmarking
> > with Arch Linux's configuration (I measure 9% with hyperfine):
>
> As nothing more is compiled, I guess this is just the additional
> packaging.
>
> > Benchmark 1: pacman-pkg @ 21b136cc63d2 ("minmax: fix up min3() and max3() too")
> >   Time (mean ± σ):     579.541 s ±  0.585 s    [User: 22156.731 s, System: 3681.698 s]
> >   Range (min … max):   578.894 s … 580.033 s    3 runs
> >
> > Benchmark 2: pacman-pkg @ c5af4db0563b ("kbuild: add debug package to pacman PKGBUILD")
> >   Time (mean ± σ):     633.419 s ±  0.972 s    [User: 22247.886 s, System: 3673.879 s]
> >   Range (min … max):   632.302 s … 634.070 s    3 runs
> >
> > Summary
> >   pacman-pkg @ 21b136cc63d2 ("minmax: fix up min3() and max3() too") ran
> >     1.09 ± 0.00 times faster than pacman-pkg @ c5af4db0563b ("kbuild: add debug package to pacman PKGBUILD")
> >
> > It would be nice to add some option to avoid building this package for
> > developers who may not want it (I know I personally would not want it
> > with that penalty because I do a lot of bisects) or maybe adding a
> > target to build this package with the rest like 'pacman-pkg-with-dbg' or
> > something? Also, couldn't vmlinux be obtained from vmlinuz that already
> > exists in the main package via scripts/extract-vmlinux?
>
> Jose:
>
> In the vanilla PKGBUILD vmlinux is part of the linux-headers package:
> linux-headers /usr/lib/modules/6.10.2-arch1-1/build/vmlinux
>
> Given that you already gate the new -debug package on CONFIG_MODULES,
> why not add the file to that package?


I do not know why CONFIG_MODULES controls the debug package.

If this is really for debugging purposes, CONFIG_DEBUG_INFO is more suitable.
Without CONFIG_DEBUG_INFO, vmlinux contains only limited amount of
information.


scripts/package/mkdebian use CONFIG_DEBUG_INFO to enable
the debug package.






-- 
Best Regards
Masahiro Yamada