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From: Namhyung Kim <namhyung@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@kernel.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>, 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: Tue, 17 Sep 2024 14:58:52 -0700	[thread overview]
Message-ID: <Zun7nKFzWz2J2rSz@google.com> (raw)
In-Reply-To: <20240916184645.142face1@rorschach.local.home>

Hello,

On Mon, Sep 16, 2024 at 06:46:45PM -0400, Steven Rostedt wrote:
> On Mon, 16 Sep 2024 20:15:45 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > 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.

Well.. technically you can sample without tid.  But I'm not sure how
much it'd be useful if you collect callchains without tid.

> 
> Is that because perf uses per task buffers? Will perf know this if it
> uses a global buffer? What does perf do with "-a"?

Then it'd use per-cpu ring buffers.  But each sample would have pid/tid
pair and time so perf tools can match it with a deferred callchian.

Thanks,
Namhyung

  reply	other threads:[~2024-09-17 21:59 UTC|newest]

Thread overview: 51+ 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
2024-09-14 14:07   ` kernel test robot
2024-09-15 12:18   ` Dan Carpenter
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  7:40   ` kernel test robot
2024-09-14  8:12   ` kernel test robot
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
2024-09-14 16:25   ` kernel test robot
2024-09-15 12:20   ` Dan Carpenter
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
2024-09-14  8:22   ` kernel test robot
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
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 [this message]
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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