linux-kernel - Re: [RFC] btf: Some structs are doubled because of struct ring

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Message-ID: <20191213184621.GG2844@hirez.programming.kicks-ass.net>
Date:   Fri, 13 Dec 2019 19:46:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        Quentin Monnet <quentin.monnet@...ronome.com>
Subject: Re: [RFC] btf: Some structs are doubled because of struct ring_buffer

On Fri, Dec 13, 2019 at 01:29:41PM -0500, Steven Rostedt wrote:
> On Fri, 13 Dec 2019 19:02:23 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:

> > Your ring buffer was so generic that I gave up trying to use it after
> > trying for days :-( (the fundamental problem was that it was impossible
> > to have a single cpu buffer; afaik that is still true today)
> 
> Yeah, but that could have been fixed, and the only reason it's not
> today, is because it requires more overhead to do so.
> 
> IIRC, the main reason that you didn't use it then, is because it wasn't
> fully lockless at the time (it is today), and you couldn't use it from
> NMI context.

What I remember is that I couldn't get a single cpu buffer, the whole
per-cpu stuff was mangled in at the wrong layer. But who knows, my
memory is faulty.


> > How about we rename both? I'm a bit adverse to long names, so how about
> > we rename the perf one to perf_buffer and the trace one to trace_buffer?
> 
> I'm fine with this idea! Now what do we call the ring buffer that
> tracing uses, as it is not specific for tracing, it was optimized for
> splicing. But sure, I can rename it to trace_buffer. I just finished
> renaming perf's...
> 
> Thinking about this, perhaps we should remove the word "ring" from
> both. That is:
> 
>   perf_buffer and trace_buffer ?

That's what I just proposed, right? So ACK on that ;-)