From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
x86@kernel.org, Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-kernel@vger.kernel.org,
Indu Bhagat <indu.bhagat@oracle.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
linux-perf-users@vger.kernel.org, Mark Brown <broonie@kernel.org>,
linux-toolchains@vger.kernel.org, Jordan Rome <jordalgo@meta.com>,
Sam James <sam@gentoo.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH v2 00/11] unwind, perf: sframe user space unwinding, deferred perf callchains
Date: Mon, 16 Sep 2024 20:15:45 +0200 [thread overview]
Message-ID: <20240916181545.GD4723@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20240916153953.7fq5fmch5uqg7tjj@treble>
On Mon, Sep 16, 2024 at 05:39:53PM +0200, Josh Poimboeuf wrote:
> The cookie is incremented once per entry from userspace, when needed.
>
> It's a unique id used by the tracers which is emitted with both kernel
> and user stacktrace samples so the userspace tool can stitch them back
> together. Even if you have multiple tracers triggering at the same time
> they can all share a single user trace.
But perf don't need this at all, right? It knows that the next deferred
trace for that tid will be the one.
> > This scheme seems unsound
> > pin yourself on CPU0 and trigger 1<<48 unwinds while keeping CPU1 idle.
>
> Hm???
The point being that it is possible to wrap one CPU into the id space of
another CPU. It is not trivial, but someone who wants to can make it
happen.
Combined I don't see the need to force this into this scheme, carry an
opaque (void*) pointer and let the user do whatever it wants, perf for
instance can pass NULL and not do anything like this.
next prev parent reply other threads:[~2024-09-16 18:16 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-13 23:02 [PATCH v2 00/11] unwind, perf: sframe user space unwinding, deferred perf callchains Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 01/11] unwind: Introduce generic user space unwinding interface Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 02/11] unwind/x86: Add HAVE_USER_UNWIND Josh Poimboeuf
2024-09-16 11:46 ` Peter Zijlstra
2024-10-20 8:09 ` Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 03/11] unwind: Introduce SFrame user space unwinding Josh Poimboeuf
2024-09-14 11:23 ` Steven Rostedt
2024-10-01 18:20 ` Indu Bhagat
2024-10-01 18:36 ` Steven Rostedt
2024-10-02 8:18 ` Florian Weimer
2024-10-02 14:05 ` Steven Rostedt
2024-10-23 13:59 ` Jens Remus
2024-10-27 17:49 ` Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 04/11] unwind/x86/64: Add HAVE_USER_UNWIND_SFRAME Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 05/11] perf/x86: Use user_unwind interface Josh Poimboeuf
2024-09-16 6:48 ` kernel test robot
2024-09-17 22:01 ` Namhyung Kim
2024-09-13 23:02 ` [PATCH v2 06/11] perf: Remove get_perf_callchain() 'init_nr' argument Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 07/11] perf: Remove get_perf_callchain() 'crosstask' argument Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 08/11] perf: Simplify get_perf_callchain() user logic Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 09/11] perf: Introduce deferred user callchains Josh Poimboeuf
2024-09-17 22:07 ` Namhyung Kim
2024-09-13 23:02 ` [PATCH v2 10/11] perf/x86: Add HAVE_PERF_CALLCHAIN_DEFERRED Josh Poimboeuf
2024-09-13 23:02 ` [PATCH v2 11/11] perf/x86: Enable SFrame unwinding for deferred user callchains Josh Poimboeuf
2024-09-14 12:12 ` [PATCH v2 00/11] unwind, perf: sframe user space unwinding, deferred perf callchains Steven Rostedt
2024-09-15 11:11 ` Josh Poimboeuf
2024-09-15 11:38 ` Steven Rostedt
2024-09-16 14:08 ` Peter Zijlstra
2024-09-16 15:39 ` Josh Poimboeuf
2024-09-16 18:15 ` Peter Zijlstra [this message]
2024-09-16 0:15 ` Mathieu Desnoyers
2024-09-16 0:33 ` Mathieu Desnoyers
2024-09-17 0:37 ` Mathieu Desnoyers
2024-09-16 22:46 ` Steven Rostedt
2024-09-17 21:58 ` Namhyung Kim
2024-09-18 5:14 ` Mathieu Desnoyers
2024-10-03 2:31 ` Steven Rostedt
2024-10-03 2:37 ` Josh Poimboeuf
2024-10-03 14:56 ` Steven Rostedt
2024-09-16 16:03 ` Steven Rostedt
2024-09-14 19:37 ` Namhyung Kim
2024-10-23 13:22 ` Jens Remus
2024-10-24 2:22 ` Steven Rostedt
2024-10-27 17:24 ` Josh Poimboeuf
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