Re: [RFC] btf: Some structs are doubled because of struct ring_buffer

From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
	"Jiri Olsa" <jolsa@redhat.com>,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Andrii Nakryiko" <andrii.nakryiko@gmail.com>,
	"Jiri Olsa" <jolsa@kernel.org>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	"Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"Andrii Nakryiko" <andriin@fb.com>,
	"Quentin Monnet" <quentin.monnet@netronome.com>
Subject: Re: [RFC] btf: Some structs are doubled because of struct ring_buffer
Date: Fri, 13 Dec 2019 19:46:21 +0100	[thread overview]
Message-ID: <20191213184621.GG2844@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20191213132941.6fa2d1bd@gandalf.local.home>

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@infradead.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 ;-)