linux-kernel - Re: [PATCH v1] trace-cmd: introduce --initital-delay for record command

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Message-ID: <20171218104158.22519a7e@gandalf.local.home>
Date:   Mon, 18 Dec 2017 10:41:58 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Trace Devel <linux-trace-devel@...r.kernel.org>
Subject: Re: [PATCH v1] trace-cmd: introduce --initital-delay for record
 command

On Mon, 18 Dec 2017 12:24:12 +0100
David Hildenbrand <david@...hat.com> wrote:

> If recording a big number of events to a big buffer, one might want to
> minimize the trace-cmd activity for a certain period in time.
> Especially, don't see any trace-cmd activity for some time. If there are
> a lot of events, the loop might actually never sleep, resulting in the
> "-s" option never becomming active.
> 
> E.g. I am using scheduler events to trace thread activity per CPU. Esp.
> sched:sched_wakeup and sched:sched_stat_runtime. Even when setting the
> sleep time to something huge like 30 seconds, I can see constant activity
> from the trace-cmd tasks.

Thanks for reporting this. Honestly, I believe this is fixing a symptom
of a real problem. I'd like to investigate why trace-cmd is running
with a sleep time of 30 seconds. I think that should be fixed.

-- Steve