From: Peter Zijlstra <peterz@infradead.org>
To: Ze Gao <zegao2021@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Namhyung Kim <namhyung@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
Jiri Olsa <jolsa@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
linux-trace-devel@vger.kernel.org, Ze Gao <zegao@tencent.com>
Subject: Re: [RFC PATCH v2 1/3] sched, tracing: add to report task state in symbolic chars
Date: Mon, 31 Jul 2023 11:36:55 +0200 [thread overview]
Message-ID: <20230731093655.GC29590@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20230726121618.19198-2-zegao@tencent.com>
On Wed, Jul 26, 2023 at 08:16:16PM +0800, Ze Gao wrote:
> Internal representations of task state are likely to be changed or
> ordered, and reporting them to userspace without exporting them as
> part of API is not a good choice, which can easily break a userspace
> observability tool as kernel evolves. For example, perf suffers from
> this and still reports wrong states by this patch.
>
> OTOH, some masqueraded state like TASK_REPORT_IDLE and TASK_REPORT_MAX
> are also reported inadvertently, which confuses things even more.
>
> So add a new variable in company with the old raw value to report task
> state in symbolic char, which is self-explaining and no further
> translation is needed, and also report priorities in 'short' to save
> some buffer space. Of course this does not break any userspace tool.
>
> Note for PREEMPT_ACTIVE, we introduce 'p' to report it and use the old
> conventions for the rest.
So I really dont much like this. This looses the ability to see the
actual wait state flags, there could be multiple. Eg, things like
TASK_FREEZEABLE gets lost completely.
And this is on top of my reluctance to touch any of this at all, for
fear of further regressions.
next prev parent reply other threads:[~2023-07-31 9:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-26 12:16 [RFC PATCH v2 0/3] report task state in symbolic chars from sched tracepoint Ze Gao
2023-07-26 12:16 ` [RFC PATCH v2 1/3] sched, tracing: add to report task state in symbolic chars Ze Gao
2023-07-31 9:36 ` Peter Zijlstra [this message]
2023-07-31 10:17 ` Ze Gao
2023-07-31 11:00 ` Ze Gao
2023-07-31 15:38 ` Steven Rostedt
2023-08-01 1:35 ` Ze Gao
2023-07-26 12:16 ` [RFC PATCH v2 2/3] perf sched: use the new prev_state_char instead in tracepoint sched_switch Ze Gao
2023-07-26 12:16 ` [RFC PATCH v2 3/3] libtraceevent: " Ze Gao
2023-07-31 15:40 ` Steven Rostedt
2023-08-01 1:36 ` Ze Gao
2023-07-28 17:29 ` [RFC PATCH v2 0/3] report task state in symbolic chars from sched tracepoint Ian Rogers
2023-07-31 2:09 ` Ze Gao
2023-07-31 3:52 ` Masami Hiramatsu
2023-07-31 6:19 ` Ze Gao
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