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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ivan Babrou <ibobrik@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>, Paul Turner <pjt@google.com>,
	Mike Galbraith <efault@gmx.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/3] sched/fair: add tracepoints for cfs throttle
Date: Thu, 24 May 2018 15:23:28 -0700	[thread overview]
Message-ID: <CAM_iQpUKTbk0Gfv5ZXWtXDF_OdJQEP8nWacAdwdv0EBCcZ+c=g@mail.gmail.com> (raw)
In-Reply-To: <20180524071152.GB12198@hirez.programming.kicks-ass.net>

On Thu, May 24, 2018 at 12:11 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> The problem with tracepoints is that they can become ABI and you cannot
> change them without breaking tools. This is a crap situation and I'm fed
> up with it.

Yeah, I once used perf_event_open() to parse the trace events, I
understand how painful it is. Fortunately tools like bcc mostly hides
the ABI from end user. To be fair, kprobe has the same problem if not
worse, different compilers could inline different kernel functions, not
to mention kernel functions could change at any time.

OTOH, the tracepoint text interface is sufficient to help people to inspect
kernel internals, like in this case I can observe when a cpu cgroup is
throttled or unthrottled. Of course they are not friendly for programming.

Thanks.

      reply	other threads:[~2018-05-24 22:23 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-22  6:20 [PATCH 0/3] sched/fair: improve CFS throttle Cong Wang
2018-05-22  6:20 ` [PATCH 1/3] sched/fair: make CFS bandwidth slice per cpu group Cong Wang
2018-05-22  6:20 ` [PATCH 2/3] sched/fair: accumulate unused cpu time for CFS throttle Cong Wang
2018-05-22  6:20 ` [PATCH 3/3] sched/fair: add tracepoints for cfs throttle Cong Wang
     [not found]   ` <CANWdNRCQCteO7L+Of7T2vWBW7GbMHyvyF5aSQMVYNGg_afxNhg@mail.gmail.com>
2018-05-23  0:34     ` Cong Wang
2018-05-23  9:09     ` Peter Zijlstra
2018-05-24  4:40       ` Cong Wang
2018-05-24  7:11         ` Peter Zijlstra
2018-05-24 22:23           ` Cong Wang [this message]

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