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From: Matthew Wilcox <willy@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org,
	npiggin@gmail.com, linux-arch@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux@armlinux.org.uk, heiko.carstens@de.ibm.com,
	riel@surriel.com, tony.luck@intel.com
Subject: Re: [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish()
Date: Wed, 20 Feb 2019 07:02:53 -0800
Message-ID: <20190220150253.GH12668@bombadil.infradead.org> (raw)
In-Reply-To: <20190220144705.GH7523@fuggles.cambridge.arm.com>

On Wed, Feb 20, 2019 at 02:47:05PM +0000, Will Deacon wrote:
> On Tue, Feb 19, 2019 at 02:41:47PM +0100, Peter Zijlstra wrote:
> > On Tue, Feb 19, 2019 at 12:47:38PM +0000, Will Deacon wrote:
> > > Fine for now, but I agree that we should drop the hook altogether. AFAICT,
> > > this only exists to help an ia64 optimisation which looks suspicious to
> > > me since it uses:
> > > 
> > >     mm == current->active_mm && atomic_read(&mm->mm_users) == 1
> > > 
> > > to identify a "single-threaded fork()" and therefore perform only local TLB
> > > invalidation. Even if this was the right thing to do, it's not clear to me
> > > that tlb_migrate_finish() is called on the right CPU anyway.
> > > 
> > > So I'd be keen to remove this hook before it spreads, but in the meantime:
> > 
> > Agreed :-)
> > 
> > The obvious slash and kill patch ... untested
> 
> I'm also unable to test this, unfortunately. Can we get it into next after
> the merge window and see if anybody reports issues?

While I do have a pair of Itanium systems in my basement, neither are
sn2 machines, which was the only sub-architecture that implemented
tlb_migrate_finish().  I see NASA decomissioned Columbia in 2013, and
I imagine most sn2 machines have been similarly scrapped.


  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-19 10:31 [PATCH v6 00/18] generic mmu_gather patches Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 01/18] asm-generic/tlb: Provide a comment Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 02/18] asm-generic/tlb: Provide HAVE_MMU_GATHER_PAGE_SIZE Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 03/18] asm-generic/tlb: Provide generic VIPT cache flush Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 04/18] asm-generic/tlb: Provide generic tlb_flush() based on flush_tlb_range() Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 05/18] asm-generic/tlb: Provide generic tlb_flush() based on flush_tlb_mm() Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:31 ` [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish() Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 13:41     ` Peter Zijlstra
2019-02-20 14:47       ` Will Deacon
2019-02-20 15:02         ` Matthew Wilcox [this message]
2019-02-19 10:31 ` [PATCH v6 07/18] asm-generic/tlb: Invert HAVE_RCU_TABLE_INVALIDATE Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 08/18] arm/tlb: Convert to generic mmu_gather Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 09/18] ia64/tlb: Conver " Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-21  2:52   ` Souptick Joarder
2019-02-19 10:31 ` [PATCH v6 10/18] sh/tlb: Convert SH " Peter Zijlstra
2019-12-03 11:19   ` Geert Uytterhoeven
2019-12-04 10:47     ` Peter Zijlstra
2019-12-04 12:32       ` Geert Uytterhoeven
2019-12-04 13:22         ` Guenter Roeck
2019-12-04 15:17           ` Geert Uytterhoeven
2019-12-04 19:03             ` Guenter Roeck
2019-12-04 13:34         ` Peter Zijlstra
2019-12-04 15:07           ` Geert Uytterhoeven
2019-12-04 16:41             ` Peter Zijlstra
2019-12-05 15:26               ` Geert Uytterhoeven
2019-12-05 19:24       ` Rob Landley
2019-12-05 19:23         ` Rich Felker
2019-12-05 19:30       ` John Paul Adrian Glaubitz
2019-12-05 22:56         ` Guenter Roeck
2019-12-06 13:38           ` John Paul Adrian Glaubitz
2019-12-06 14:03             ` Guenter Roeck
2019-02-19 10:31 ` [PATCH v6 11/18] um/tlb: Convert " Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 12/18] arch/tlb: Clean up simple architectures Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 13/18] asm-generic/tlb: Introduce HAVE_MMU_GATHER_NO_GATHER Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:32 ` [PATCH v6 14/18] s390/tlb: convert to generic mmu_gather Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:32 ` [PATCH v6 15/18] asm-generic/tlb: Remove arch_tlb*_mmu() Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 16/18] asm-generic/tlb: Remove HAVE_GENERIC_MMU_GATHER Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 17/18] asm-generic/tlb: Remove tlb_flush_mmu_free() Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 18/18] asm-generic/tlb: Remove tlb_table_flush() Peter Zijlstra

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