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Subject: Re: [PATCH RFC] remove jump_label optimization for perf sched events
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Gleb Natapov <gleb@redhat.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
        Jason Baron <jbaron@redhat.com>, rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 17 Nov 2011 14:10:12 +0100
In-Reply-To: <20111117130032.GC16853@redhat.com>
References: <20111117123029.GB16853@redhat.com>
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On Thu, 2011-11-17 at 15:00 +0200, Gleb Natapov wrote:

> > That said, I'd much rather throttle this particular jump label than
> > remove it altogether, some people really don't like all this scheduler
> > hot path crap.
> What about moving perf_event_task_sched() to sched_(in|out)_preempt_notifiers?
> preempt notifiers checking is already on the scheduler hot path, so no
> additional overhead for perf case.

Same problem really, some people complain about the overhead of preempt
notifiers, also not all kernels have those in. 

Futhermore I loathe notifier lists because they obscure wtf is done.