linux-kernel - Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

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Message-Id: <20170727144634.GY3730@linux.vnet.ibm.com>
Date:   Thu, 27 Jul 2017 07:46:34 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, will.deacon@....com
Subject: Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

On Thu, Jul 27, 2017 at 04:36:24PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 27, 2017 at 07:32:05AM -0700, Paul E. McKenney wrote:
> > > as per your proposed patch, will spray IPIs to all CPUs and at high
> > > rates.
> > 
> > OK, I have updated my patch to do throttling.
> 
> But not respect cpusets. Which is the other important point.
> 
> The scheduler based IPIs are limited to where we are allowed to place
> tasks (as are the TLB ones for that matter, for the exact same reason).

Yes, these are disadvantages, no argument there.  But I will nevertheless
be carrying some variant of this patch until something better exists,
including that something being tested and found satisfactory by the
various people asking for this.

							Thanx, Paul