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Date: Tue, 17 May 2022 21:37:49 -0700
From: Ian Rogers <irogers@...gle.com>
To: John Garry <john.garry@...wei.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Kan Liang <kan.liang@...ux.intel.com>,
Andi Kleen <ak@...ux.intel.com>,
Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
Felix Fietkau <nbd@....name>, Qi Liu <liuqi115@...wei.com>,
Like Xu <likexu@...cent.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Nick Forrington <nick.forrington@....com>,
Kajol Jain <kjain@...ux.ibm.com>,
James Clark <james.clark@....com>,
Andrew Kilroy <andrew.kilroy@....com>,
"Paul A . Clarke" <pc@...ibm.com>, Will Deacon <will@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
ananth.narayan@....com, ravi.bangoria@....com,
santosh.shukla@....com, sandipan.das@....com,
Caleb Biggers <caleb.biggers@...el.com>,
Perry Taylor <perry.taylor@...el.com>,
Kshipra Bopardikar <kshipra.bopardikar@...el.com>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 6/7] perf jevents: Switch build to use jevents.py
On Tue, May 17, 2022 at 3:32 AM John Garry <john.garry@...wei.com> wrote:
>
> On 13/05/2022 16:58, Ian Rogers wrote:
> > On Fri, May 13, 2022 at 8:38 AM John Garry <john.garry@...wei.com> wrote:
> >>
> >> On 11/05/2022 22:15, Ian Rogers wrote:
> >>> # jevents.py uses os.scandir and type hints present in Python 3.5 released in Sept. 2015.
> >>> + JEVENTS_PYTHON_GOOD := $(shell $(PYTHON) -c 'import sys;print("1" if(sys.version_info.major >= 3 and sys.version_info.minor >= 5) else "0")')
> >>
> >> I think that many - like me - will have python 2.7, so now will find no
> >> pmu-events generated any longer after missing this message in the build :(
> >>
> >> Maybe many will have python >= 3.5 - but I don't know...
> >
> > So Python 2 has been end-of-life for over 2 years now:
> > https://www.python.org/doc/sunset-python-2/
> > There have been a number of LKML patches upgrading python to version 3.
> >
> > Python 3.5 has some very nice features of os.scandir and type hints,
> > so if I set the bar lower than this it hurts the code quality. It is
> > also at least 6 years old at this point, and so hopefully not
> > unreasonable for a distribution to have picked it up :-) Looking at
> > the change to C11 thread:
> > https://lore.kernel.org/lkml/20220228103142.3301082-1-arnd@kernel.org/
> > It seems the motivation for picking a language version is the features
> > it provides and compatibility. If we choose pre-Python 3.5 we get more
> > compatibility but we lose language features.
> >
> > My feeling is that we shouldn't need to support things that are no
> > longer maintained (like Python 2) but I'm less clear if Python 3.5 is
> > sufficiently compatible for everyone's needs. I kind of hope so, hence
> > making the patches this way.
>
> Fine, I just think that you need to make this transition as seamless as
> possible, otherwise it can be judged as a regression.
Agreed.
> For example, I have now python 3.6 (default) and 2.7 but it still
> doesn't seem to work:
>
> john@...alhost:~/acme/tools/perf> make
> BUILD: Doing 'make -j4' parallel build
> Warning: Kernel ABI header at 'tools/include/linux/coresight-pmu.h'
> differs from latest version at 'include/linux/coresight-pmu.h'
> diff -u tools/include/linux/coresight-pmu.h include/linux/coresight-pmu.h
> Makefile.config:593: No sys/sdt.h found, no SDT events are defined,
> please install systemtap-sdt-devel or systemtap-sdt-dev
> Makefile.config:871: Python interpreter too old (older than 3.5)
> disabling jevent generation
> Makefile.config:904: Old version of libbfd/binutils things like PE
> executable profiling will not be available
> Makefile.config:1092: No openjdk development package found, please
> install JDK package, e.g. openjdk-8-jdk, java-1.8.0-openjdk-devel
>
> Auto-detecting system features:
> ... dwarf: [ on ]
> ... dwarf_getlocations: [ on ]
> ... glibc: [ on ]
> ... libbfd: [ OFF ]
> ... libbfd-buildid: [ OFF ]
> ... libcap: [ on ]
> ... libelf: [ on ]
> ... libnuma: [ on ]
> ... numa_num_possible_cpus: [ on ]
> ... libperl: [ on ]
> ... libpython: [ on ]
> ... libcrypto: [ on ]
> ... libunwind: [ on ]
> ... libdw-dwarf-unwind: [ on ]
> ... zlib: [ on ]
> ... lzma: [ on ]
> ... get_cpuid: [ on ]
> ... bpf: [ on ]
> ... libaio: [ on ]
> ... libzstd: [ on ]
> ... disassembler-four-args: [ on ]
>
>
> make[3]: Nothing to be done for 'install_headers'.
> john@...alhost:~/acme/tools/perf> python --version
> Python 3.6.12
> john@...alhost:~/acme/tools/perf>
>
> which I need to figure out...
Yep, I can't explain that :-) You could try something like adding a
$(warning ... or similar to the build and running:
python3 -c 'import sys; print(sys.version_info)'
the jevents.py uses f-strings and so I'll need to bump the version
from 3.5 to 3.6 in v2. Python 3.6 was released in December 2016.
Thanks,
Ian
> >
> >> > + ifneq ($(JEVENTS_PYTHON_GOOD), 1)
> >> > + $(warning Python interpreter too old (older than 3.5) disabling
> >> jevent generation)
> >> > + NO_JEVENTS := 1
> >>
> >> It is possible to flip NO_JEVENTS to be JEVENTS, i.e. no
> >> double-negatives, like NO_JEVENTS := 0
> >
> > Agreed that double negatives are bad. The NO_... pattern is kind of
> > throughout the make files and build files. I preferred the NO_... for
> > consistency but if there's a consensus I'm happy to change.
> >
>
> I have no strong preference. I just find that double negatives boggle
> the mind.
>
> Thanks,
> john
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