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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Will Deacon <will.deacon@arm.com>, Peter Zijlstra <peterz@infradead.org>
Cc: torvalds@linux-foundation.org, oleg@redhat.com,
	paulmck@linux.vnet.ibm.com, mpe@ellerman.id.au,
	npiggin@gmail.com, linux-kernel@vger.kernel.org,
	mingo@kernel.org, stern@rowland.harvard.edu,
	Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>
Subject: Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending()
Date: Thu, 03 Aug 2017 08:54:40 +1000	[thread overview]
Message-ID: <1501714480.2664.10.camel@kernel.crashing.org> (raw)
In-Reply-To: <20170802090220.GE15219@arm.com>

On Wed, 2017-08-02 at 10:02 +0100, Will Deacon wrote:
> > > So flush_tlb_range is actually weaker than smp_mb in some respects, yet the
> > > flush_tlb_pending stuff will still work correctly.
> > 
> > So while I think you're right, and we could live with this, after all,
> > if we know the mm is CPU local, there shouldn't be any SMP concerns wrt
> > its page tables. Do you really want to make this more complicated?
> 
> It gives us a nice performance lift on arm64 and I have a patch...[1]

We do that on powerpc too, though there are ongoing questions a to
whether an smp_mb() after setting the mask bit in switch_mm is
sufficient vs. prefetch brining entries in the TLB after the context is
switched. But that's a powerpc specific issue. Nick Piggin is working
on sorting that out.

Cheers,
Ben.

  reply	other threads:[~2017-08-03  2:34 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-07 16:15 [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra
2017-06-09 14:45   ` Will Deacon
2017-06-09 18:42     ` Peter Zijlstra
2017-07-28 17:45     ` Peter Zijlstra
2017-08-01 10:31       ` Will Deacon
2017-08-01 12:02         ` Benjamin Herrenschmidt
2017-08-01 12:14           ` Peter Zijlstra
2017-08-01 16:39             ` Peter Zijlstra
2017-08-01 16:44               ` Will Deacon
2017-08-01 16:48                 ` Peter Zijlstra
2017-08-01 22:59                   ` Peter Zijlstra
2017-08-02  1:23                     ` Benjamin Herrenschmidt
2017-08-02  8:11                       ` Peter Zijlstra
2017-08-02  8:15                         ` Will Deacon
2017-08-02  8:43                           ` Will Deacon
2017-08-02  8:51                             ` Peter Zijlstra
2017-08-02  9:02                               ` Will Deacon
2017-08-02 22:54                                 ` Benjamin Herrenschmidt [this message]
2017-08-02  8:45                           ` Peter Zijlstra
2017-08-02  9:02                             ` Will Deacon
2017-08-02  9:18                               ` Peter Zijlstra
2017-08-02 13:57                         ` Benjamin Herrenschmidt
2017-08-02 15:46                           ` Peter Zijlstra
2017-08-02  0:17                   ` Benjamin Herrenschmidt
2017-08-01 22:42             ` Benjamin Herrenschmidt
2017-06-07 16:15 ` [RFC][PATCH 2/5] locking: Introduce smp_mb__after_spinlock() Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 4/5] locking: Remove smp_mb__before_spinlock() Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra
2017-06-08  0:32   ` Nicholas Piggin
2017-06-08  6:54     ` Peter Zijlstra
2017-06-08  7:29       ` Nicholas Piggin
2017-06-08  7:57         ` Peter Zijlstra
2017-06-08  8:21           ` Nicholas Piggin
2017-06-08  9:54           ` Michael Ellerman
2017-06-08 10:00             ` Nicholas Piggin
2017-06-08 12:45               ` Peter Zijlstra
2017-06-08 13:18                 ` Nicholas Piggin
2017-06-08 13:47                   ` Peter Zijlstra
2017-06-09 14:49 ` [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Will Deacon

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