linux-kernel - Re: [PATCH 0/7] Rewrite jevents program in python

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Message-ID: <20220511135605.GA76023@worktop.programming.kicks-ass.net>
Date:   Wed, 11 May 2022 15:56:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     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>,
        John Garry <john.garry@...wei.com>,
        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 0/7] Rewrite jevents program in python

On Wed, May 11, 2022 at 06:50:59AM -0700, Ian Rogers wrote:
> On Wed, May 11, 2022 at 12:35 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Wed, May 11, 2022 at 12:01:26AM -0700, Ian Rogers wrote:
> >
> > > The changes here switch from jevents.c to a rewrite in python called
> > > jevents.py. This means there is a build time dependency on python, but
> > > such a dependency already exists for asciidoc (used to generate perf's
> > > man pages).
> >
> > You mean just building perf (not the docs) will now require snake stuff?
> >
> > That's very tedious :/ I don't typically have snakes on my machines.
> 
> Hi Peter,
> 
> You're right that after these changes python is a build requirement
> for jevents. We could keep the C code around for the case that python
> isn't there, but I want to do things like remove the string
> relocations, sort the events by name so we don't linearly search, etc.
> which would be a massive chore to keep alive on the C side. An
> alternative would be to have an empty pmu-events.c file that is used
> for this case. If you wanted to keep things in C and have jevents like
> event names, you could use the empty version and link in libpfm4.

I'm not normally linking to libpfm4. All I really care about is that I
can still build a bare cli perf (not even tui). If all the snake stuff
is purely optional and it just disables some features, but I do get a
perf out at the end, then I'm all good.