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From: Itai Handler <itai.handler@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: aarch64 boot time increases with rt
Date: Thu, 16 Jul 2020 16:04:12 +0300	[thread overview]
Message-ID: <CAFpOueQ1g1puaDBnmda6ZXq4sEXBjOBHr=m09-DEX9EvdwAQPg@mail.gmail.com> (raw)
In-Reply-To: <20200715153632.3f9dc5d3@oasis.local.home>

Hi Steven,

On Wed, Jul 15, 2020 at 10:36 PM Steven Rostedt <rostedt@goodmis.org> wrote:

> To rule out that this may be an issue with the function_graph tracer,
> can you also try it with:
>
>  ftrace=function ftrace_filter=worqueue_prepare_cpu
>
> And see if the function tracer shows anything.
>
> /me just looked at the code.
>
> Yes, the function tracer is set up to trace really early, but the
> function_graph tracer is initialized by core_initcall(), which is much
> later.
>
> Perhaps try this patch (note, it's from latest mainline):
>
> And retry the function_graph tracer.

With this patch, the function graph tracer doesn't work at boot time.
Please see the log below:

# mount -t debugfs debugfs /sys/kernel/debug/
# cd /sys/kernel/debug/tracing/trace
# cat current_tracer
nop

Note that I tested it both on 5.4.47-rt28 and 5.6.19-rt11 (but not on
latest mainline).

Regarding the function tracer, you were correct: it can trace
workqueue_prepare_cpu
without any issue.

Thank you,
Itai Handler

      reply	other threads:[~2020-07-16 13:04 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 14:56 aarch64 boot time increases with rt Itai Handler
2020-07-14  1:20 ` Steven Rostedt
2020-07-14 12:18   ` Itai Handler
2020-07-14 14:34     ` Steven Rostedt
2020-07-15 19:36     ` Steven Rostedt
2020-07-16 13:04       ` Itai Handler [this message]

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