linux-kernel - Re: [POC][RFC][PATCH 0/3] tracing: Add perf events to trace buffer

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Message-ID: <20251118085733.2a9ce5b0@gandalf.local.home>
Date: Tue, 18 Nov 2025 08:57:33 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...nel.org>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, Thomas
 Gleixner <tglx@...utronix.de>, Ian Rogers <irogers@...gle.com>, Namhyung
 Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri
 Olsa <jolsa@...nel.org>, Douglas Raillard <douglas.raillard@....com>
Subject: Re: [POC][RFC][PATCH 0/3] tracing: Add perf events to trace buffer

On Tue, 18 Nov 2025 08:53:24 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> > Yes, so if user adds more than that, it will return -ENOSPC.  
> 
> The issue is that the ids are defined by what is possible, not by what the
> user enables.

Now we could take 4 more bits from the mask and bring the raw value down to
just 52 bits. 2^51 at 4GHz is still 6 days. Which is plenty more than required.

This will make the id 12 bits, or 4096 different defined events.

-- Steve