From: Peter Zijlstra <peterz@infradead.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-kernel@vger.kernel.org, x86@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
Subject: Re: [PATCH RFC 04/10] perf: Introduce deferred user callchains
Date: Mon, 13 Nov 2023 18:21:06 +0100 [thread overview]
Message-ID: <20231113172106.GA12501@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CAM9d7chgoiwc3ZfQ8SzO7gV0oQOKMK3bJAdxa63Pzgcqo4i7tQ@mail.gmail.com>
On Mon, Nov 13, 2023 at 08:56:39AM -0800, Namhyung Kim wrote:
> Ok, then BPF gets no user call stacks even with sframes.
Well, you could obviously run another BPF program at return to user and
stitch there.
> Ok, but ...
> If the task is preempted, the call stack would be from another
> task (if it also has the pending call stacks) and we need to
> check which user call stack matches which kernel call stack.
> So there's no guarantee we can just use adjacent samples.
So upon requesting a user backtrace for the task it could request a
token (from eg a global atomic u64 in the most crude case) and place
this in the task_struct. The backtrace will emit this as forward
reference for the user trace.
Once the task_work generates the user stacktrace, it will again dump
this token along with the user unwind, after which it will reset the
token for this this task (to 0).
next prev parent reply other threads:[~2023-11-13 17:21 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-09 0:41 [PATCH RFC 00/10] perf: user space sframe unwinding Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 01/10] perf: Remove get_perf_callchain() 'init_nr' argument Josh Poimboeuf
2023-11-11 6:09 ` Namhyung Kim
2023-11-09 0:41 ` [PATCH RFC 02/10] perf: Remove get_perf_callchain() 'crosstask' argument Josh Poimboeuf
2023-11-11 6:11 ` Namhyung Kim
2023-11-11 20:53 ` Jordan Rome
2023-11-09 0:41 ` [PATCH RFC 03/10] perf: Simplify get_perf_callchain() user logic Josh Poimboeuf
2023-11-11 6:11 ` Namhyung Kim
2023-11-09 0:41 ` [PATCH RFC 04/10] perf: Introduce deferred user callchains Josh Poimboeuf
2023-11-11 6:57 ` Namhyung Kim
2023-11-11 18:49 ` Josh Poimboeuf
2023-11-11 18:54 ` Josh Poimboeuf
2023-11-13 16:56 ` Namhyung Kim
2023-11-13 17:21 ` Peter Zijlstra [this message]
2023-11-13 17:48 ` Namhyung Kim
2023-11-13 18:49 ` Peter Zijlstra
2023-11-13 19:16 ` Namhyung Kim
2023-11-15 16:13 ` Namhyung Kim
2023-11-20 14:03 ` Peter Zijlstra
2024-09-13 13:08 ` Josh Poimboeuf
2024-09-13 13:36 ` Peter Zijlstra
2024-09-13 13:53 ` Josh Poimboeuf
2024-09-13 14:47 ` Josh Poimboeuf
2024-09-13 15:26 ` Peter Zijlstra
2023-11-09 0:41 ` [PATCH RFC 05/10] perf/x86: Add HAVE_PERF_CALLCHAIN_DEFERRED Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 06/10] unwind: Introduce generic user space unwinding interfaces Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 07/10] unwind/x86: Add HAVE_USER_UNWIND Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 08/10] perf/x86: Use user_unwind interface Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 09/10] unwind: Introduce SFrame user space unwinding Josh Poimboeuf
2023-11-09 19:31 ` Indu Bhagat
2023-11-09 19:37 ` Josh Poimboeuf
2023-11-09 19:49 ` Steven Rostedt
2023-11-09 19:53 ` Josh Poimboeuf
2023-11-09 0:41 ` [PATCH RFC 10/10] unwind/x86/64: Add HAVE_USER_UNWIND_SFRAME Josh Poimboeuf
2023-11-09 0:45 ` [PATCH RFC 00/10] perf: user space sframe unwinding Josh Poimboeuf
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