RE: Getting the latest and greatest Linux perf features on every Debian kernel

["Moessbauer, Felix" <felix.moessbauer@siemens.com>]

> -----Original Message-----
> From: Ian Rogers <irogers@google.com>
> Sent: Monday, November 22, 2021 5:57 PM
> To: Moessbauer, Felix (T RDA IOT SES-DE) <felix.moessbauer@siemens.com>
> Cc: debian-kernel@lists.debian.org; waldi@debian.org; linux-perf-users <linux-
> perf-users@vger.kernel.org>; Arnaldo Carvalho de Melo <acme@kernel.org>;
> ben@decadent.org.uk; Jiri Olsa <jolsa@kernel.org>; Namhyung Kim
> <namhyung@kernel.org>; Kiszka, Jan (T RDA IOT) <jan.kiszka@siemens.com>;
> Schild, Henning (T RDA IOT SES-DE) <henning.schild@siemens.com>; Schmidt,
> Adriaan (T RDA IOT SES-DE) <adriaan.schmidt@siemens.com>
> Subject: Re: Getting the latest and greatest Linux perf features on every Debian
> kernel
> 
> On Mon, Nov 22, 2021 at 4:54 AM Moessbauer, Felix
> <felix.moessbauer@siemens.com> wrote:
> >
> > Hi,
> >
> > > -----Original Message-----
> > > From: Ian Rogers <irogers@google.com>
> > > Sent: Monday, November 22, 2021 3:18 AM
> > > To: debian-kernel@lists.debian.org; waldi@debian.org
> > > Cc: linux-perf-users <linux-perf-users@vger.kernel.org>; Arnaldo
> > > Carvalho de Melo <acme@kernel.org>; ben@decadent.org.uk; Jiri Olsa
> > > <jolsa@kernel.org>; Namhyung Kim <namhyung@kernel.org>
> > > Subject: Re: Getting the latest and greatest Linux perf features on
> > > every Debian kernel
> > >
> > > Hi,
> > >
> > > I'd love to package Linux perf as per Arnaldo's prepared tarball for
> > > Debian. If I could get help on the Debian side it would be great!
> > > The actions that are needed
> > > are:
> > >
> > > 1) package Arnaldo's tarball for Debian, presumably the build in the
> > > sources for
> > > linux-perf-5.10 will be a good starting point. The package will be
> > > linux-perf and replace the current metapackage of the same name.
> >
> > The current packaging in Debian does not include the perf python bindings.
> > Today these bindings are used by more and more tools (e.g. tuned).
> > For that, we packaged both a versioned module (linux-perf-<...>) and a python
> wrapper to load it using 'import perf' (linux-base).
> > These patches are currently under review at Debian salsa [1].
> >
> > All this would be way simpler if perf bindings do not have to be versioned
> anymore.
> > But please also consider that still a lot of people are using 4.19er kernels (don't
> know since when versioning is no longer required).
> 
> Thanks Felix! Is there a specific bug I can look at which describes what is broken
> with later versions of perf an 4.19? Perhaps we can add a workaround for this
> age of kernel in the command. It is certainly nobody's intent to have some users
> without a workable tool. Fwiw, I do a lot of testing with an older 4.15 based
> kernel and I'm not aware of issues.

Actually I don't know of any bugs, but just wanted to point out that this kernel should still be supported.
If that works with a modern perf out of the box, that would be even better.

> > >
> > >
> > > 2) create an updated linux-base that removes /usr/bin/perf
> > >
> > > 3) upload the updated linux-base and linux-perf packages for
> > > maintainer approval to
> > >
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmentors.
> > >
> debian.net%2F&amp;data=04%7C01%7Cfelix.moessbauer%40siemens.com%7C
> > >
> 4dbf17b41e4542b4c2de08d9ad5e58c3%7C38ae3bcd95794fd4addab42e1495d5
> > >
> 5a%7C1%7C0%7C637731443001828013%7CUnknown%7CTWFpbGZsb3d8eyJWI
> > >
> joiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C300
> > >
> 0&amp;sdata=80jfnANxTuGYzw0vErMUQOlpdUWFrDNP5n9ktaVTBaQ%3D&amp
> > > ;reserved=0
> > >
> > > 4) some how get the previous Debian linux-perf-[45].* packages
> > > removed
> >
> > This can easily be achieved using the Conflicts field with a linux-base version
> that is older than your patched one.
> 
> Can I use Conflicts to say that the linux-perf package, that will provide
> /usr/bin/perf, will conflict with earlier linux-base releases?
> I'm concerned that if linux-base conflicts with linux-perf and linux-perf conflicts
> with linux-base, it is quite easy to make something that becomes wedged :-)

For details, have a look here: https://www.debian.org/doc/debian-policy/ch-relationships.html#s-replaces
You could start with the packaging (as part of the Debian Linux source package) and create a MR at Salsa [1].
Then I can have a look over it and implement the transition / replacement.

[1] https://salsa.debian.org/kernel-team/linux

Felix
 
> 
> > >
> > > After this, when Arnaldo sends out a new tarball we can update the
> > > linux-perf package. libbpf and libtraceevent are currently part of
> > > linux/tools, but it would be better to depend on the distribution
> > > versions, which can be a future update to the packaging.
> > >
> > > I'd love some feedback on this plan, whether linux-base/linux-perf
> > > have a special process, etc. Documentation wise I've seen there is a lot, but:
> > >
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmentors.
> > > debian.net%2Fintro-
> > >
> maintainers%2F&amp;data=04%7C01%7Cfelix.moessbauer%40siemens.com%7
> > >
> C4dbf17b41e4542b4c2de08d9ad5e58c3%7C38ae3bcd95794fd4addab42e1495d
> > >
> 55a%7C1%7C0%7C637731443001828013%7CUnknown%7CTWFpbGZsb3d8eyJ
> > >
> WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C
> > >
> 3000&amp;sdata=Y0L%2Bn%2B0yJqGVnp%2FhCfBVD9V3bZ%2Bffb48vy85jg92M
> > > oU%3D&amp;reserved=0
> > > looks fairly to the point.
> >
> > I really like the plan and I'm also willing to support here.
> > But please also note that I'm not a Debian sponsor or maintainer of the
> mentioned packages.
> 
> Thanks!
> Ian
> 
> > Felix
> >
> > >
> > > Thanks,
> > > Ian
> > >
> > >
> > >
> > > On Fri, Nov 12, 2021 at 6:39 AM Arnaldo Carvalho de Melo
> > > <acme@kernel.org>
> > > wrote:
> > > >
> > > > Em Thu, Nov 11, 2021 at 10:34:33PM -0800, Ian Rogers escreveu:
> > > > > Hi,
> > > >
> > > > > Debian currently tries to match the Linux perf tool to the
> > > > > version of the kernel that it is being run upon. Reaching out to
> > > > > Ben Hutchings, he explained to me that this was done back in
> > > > > 2010 due to kernel and Linux perf incompatibilities. This was
> > > > > likely the case, but it was a bug in the Linux perf tool that should have
> been fixed.
> > > > > It is the goal of the tool to be backward compatible. A problem
> > > > > with matching the tool to the kernel version is that users miss
> > > > > out on new features and fixes (this topic came up in a recent
> > > > > interview of the maintainer Arnaldo Carvalho de Melo [1]).
> > > >
> > > > > Ben Hutchings informs me that making it so that Debian ships the
> > > > > latest Linux perf tool requires updates both to the linux-base
> > > > > and linux source packages. The Linux perf tool also has many
> > > > > other often optional dependencies, like libunwind, libbpf,
> > > > > libpfm4, libtraceevent, etc. In general, having the dependency
> > > > > will unlock more
> > > features.
> > > > > Linux tools has its own copies of libbpf and libtraceevent, and
> > > > > so these may pose some versioning issues.
> > > >
> > > > We can use LIBBPF_DYNAMIC=1 to use the distro libbpf-dev package,
> > > > which currently is going thru some growing pains as libbpf is 0.x,
> > > > with several APIs being deprecated, others renamed, and that has
> > > > been a source of friction, but should be past us with v1.0. Till
> > > > then the perf codebase is being adjusted to allow it to be
> > > > seamlessly built with the in-kernel version and with whatever libbpf-devel
> the distro has.
> > > >
> > > > > I think it'd be great to get Debian shipping the latest version
> > > > > of Linux perf for its users. Hopefully we can agree to change
> > > > > how Debian packages perf currently and then work out the best
> > > > > way to package and keep it up-to-date. I look forward to everyone's help
> and input.
> > > >
> > > > I also keep the tarballs available at:
> > > >
> > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > mirr
> > > >
> > >
> ors.edge.kernel.org%2Fpub%2Flinux%2Fkernel%2Ftools%2Fperf%2F&amp;dat
> > > a=
> > > >
> > >
> 04%7C01%7Cfelix.moessbauer%40siemens.com%7C4dbf17b41e4542b4c2de08d
> > > 9ad5
> > > >
> > >
> e58c3%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637731443001
> > > 828013%
> > > >
> > >
> 7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTi
> > > I6Ik
> > > >
> > >
> 1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=A2TTg%2BElfRv9bslXw6YmEA1
> > > R8Iu08Z
> > > > hFyv6juVhRj24%3D&amp;reserved=0
> > > >
> > > > Where there are instructions on how to build this detached tarball.
> > > >
> > > > I regularly build perf on lots of distros, including:
> > > >
> > > >   debian:9                      : Ok   gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516 ,
> > > clang version 3.8.1-24 (tags/RELEASE_381/final)
> > > >   debian:10                     : Ok   gcc (Debian 8.3.0-6) 8.3.0 , clang version 7.0.1-
> > > 8+deb10u2 (tags/RELEASE_701/final)
> > > >   debian:11                     : Ok   gcc (Debian 10.2.1-6) 10.2.1 20210110 ,
> Debian
> > > clang version 11.0.1-2
> > > >   debian:experimental           : Ok   gcc (Debian 11.2.0-10) 11.2.0 , Debian
> clang
> > > version 11.1.0-4
> > > >   debian:experimental-x-arm64   : Ok   aarch64-linux-gnu-gcc (Debian
> 11.2.0-9)
> > > 11.2.0
> > > >   debian:experimental-x-mips    : Ok   mips-linux-gnu-gcc (Debian 10.2.1-6)
> > > 10.2.1 20210110
> > > >   debian:experimental-x-mips64  : Ok   mips64-linux-gnuabi64-gcc (Debian
> > > 10.2.1-6) 10.2.1 20210110
> > > >   debian:experimental-x-mipsel  : Ok   mipsel-linux-gnu-gcc (Debian 11.2.0-
> 9)
> > > 11.2.0
> > > >
> > > > Ditto for ubuntu.
> > > >
> > > > A complete list can be found in each pull request I send to Linus,
> > > > see in the last one:
> > > >
> > > >
> > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > lore
> > > > .kernel.org%2Fall%2F20211107204947.1394255-1-
> > > acme%40kernel.org%2F&amp;
> > > >
> > >
> data=04%7C01%7Cfelix.moessbauer%40siemens.com%7C4dbf17b41e4542b4c2
> > > de08
> > > >
> > >
> d9ad5e58c3%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C6377314
> > > 4300182
> > > >
> > >
> 8013%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzI
> > > iLCJBT
> > > >
> > >
> iI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=foKAv3e5lm5du1yoLqhzIVf
> > > vfc7
> > > > RkZqRAxmfTFkID9U%3D&amp;reserved=0
> > > >
> > > > Search for BUILD_TARBALL.
> > > >
> > > > There is also the output for 'make -C tools/perf build-test' that
> > > > tests building with lots of combinations of optional libraries,
> > > > for instance, with LIBBPF_DYNAMIC=1, etc.
> > > >
> > > > - Arnaldo