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From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Qais Yousef <qais.yousef@arm.com>, Ingo Molnar <mingo@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-kernel@vger.kernel.org,
	Pavankumar Kondeti <pkondeti@codeaurora.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Uwe Kleine-Konig <u.kleine-koenig@pengutronix.de>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Quentin Perret <quentin.perret@arm.com>
Subject: Re: [PATCH v3 0/6] sched: Add new tracepoints required for EAS testing
Date: Wed, 5 Jun 2019 09:22:27 +0200
Message-ID: <20190605072227.GI3419@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190605061748.GA20661@infradead.org>

On Tue, Jun 04, 2019 at 11:17:48PM -0700, Christoph Hellwig wrote:
> > The following patches add the bare minimum tracepoints required to perform EAS
> > testing in Lisa[1].
> 
> What is EAS?  Whhy is "Lisa" not part of the patch submission?
> submission.
> 
> > It is done in this way because adding new TRACE_EVENTS() is no longer accepted
> > AFAIU.
> 
> Huh?  We keep adding trace events all the time.  And they actually
> are useful because they are testable.

They also form an implicit API/ABI with userspace, and I've been bitten
by that crap before. No more tracepoints. IIRC viro is also not having
tracepoints in the vfs.

> This series on the other hand adds exports not used in tree, which is
> a big no-go.

I much prefer a few unused exports that expose data in a controlled
fashion than commit to an implicit ABI through tracepoints. By keeping
it all in kernel, we're punting to the no-in-kernel-ABI rule.

Basically nobody gives a crap if we break (out-of-tree) modules, but the
moment we break something userspace we're fscked.


  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-04 11:14 Qais Yousef
2019-06-04 11:14 ` [PATCH v3 1/6] sched: autogroup: Make autogroup_path() always available Qais Yousef
2019-06-25  8:24   ` [tip:sched/core] sched/autogroup: " tip-bot for Qais Yousef
2019-06-04 11:14 ` [PATCH v3 2/6] sched: add a new sched_trace_*() helper functions Qais Yousef
2019-06-25  8:25   ` [tip:sched/core] sched/debug: Add " tip-bot for Qais Yousef
2019-06-04 11:14 ` [PATCH v3 3/6] sched: Add new tracepoints to track pelt at rq level Qais Yousef
2019-06-25  8:26   ` [tip:sched/core] sched/debug: Add new tracepoints to track PELT " tip-bot for Qais Yousef
2019-06-04 11:14 ` [PATCH v3 4/6] sched: Add new tracepoint to track pelt at se level Qais Yousef
2019-06-25  8:27   ` [tip:sched/core] sched/debug: Add new tracepoint to track PELT " tip-bot for Qais Yousef
2019-06-04 11:14 ` [PATCH v3 5/6] sched: Add sched_overutilized tracepoint Qais Yousef
2019-06-17 15:50   ` Peter Zijlstra
2019-06-17 16:31     ` Qais Yousef
2019-06-25  8:27   ` [tip:sched/core] sched/debug: " tip-bot for Qais Yousef
2019-06-04 11:14 ` [PATCH v3 6/6] sched: export the newly added tracepoints Qais Yousef
2019-06-25  8:28   ` [tip:sched/core] sched/debug: Export " tip-bot for Qais Yousef
2019-06-05  6:17 ` [PATCH v3 0/6] sched: Add new tracepoints required for EAS testing Christoph Hellwig
2019-06-05  7:22   ` Peter Zijlstra [this message]
2019-06-05 22:33   ` Qais Yousef
2019-06-17 12:51 ` Qais Yousef
2019-06-17 15:55   ` Peter Zijlstra
2019-06-17 16:22     ` Qais Yousef

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