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Date:   Thu, 28 Jan 2021 13:17:53 +0100
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@kernel.org>, Mel Gorman <mgorman@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Michal Hocko <mhocko@suse.com>,
        ardb@kernel.org, jpoimboe@redhat.com
Subject: Re: [RFC PATCH 4/8] preempt: Introduce CONFIG_PREEMPT_DYNAMIC
Message-ID: <20210128121753.GA122776@lothringen>
References: <20210118141223.123667-1-frederic@kernel.org>
 <20210118141223.123667-5-frederic@kernel.org>
 <20210122165343.GE16371@worktop.programming.kicks-ass.net>
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On Fri, Jan 22, 2021 at 05:53:43PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 18, 2021 at 03:12:19PM +0100, Frederic Weisbecker wrote:
> > +config HAVE_PREEMPT_DYNAMIC
> > +	bool
> > +	depends on HAVE_STATIC_CALL_INLINE
> 
> I think we can relax this to HAVE_STATIC_CALL, using trampolines
> shouldn't be too bad, and that would put it in reach of arm64.

Why not, but then I need to make CONFIG_PREEMPT_DYNAMIC optional
in order not to make the overhead mandatory for everyone.

> 
> > +	depends on GENERIC_ENTRY
> > +	help
> > +	   Select this if the architecture support boot time preempt setting
> > +	   on top of static calls. It is strongly advised to support inline
> > +	   static call to avoid any overhead.