Message-ID: <1340884801.20977.84.camel@pasglop>
Subject: Re: [PATCH 02/20] mm: Add optional TLB flush to generic RCU
 page-table freeing
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@elte.hu>, akpm@linux-foundation.org,
        Rik van Riel <riel@redhat.com>,
        Hugh Dickins <hugh.dickins@tiscali.co.uk>, Mel Gorman <mel@csn.ul.ie>,
        Nick Piggin <npiggin@kernel.dk>, Alex Shi <alex.shi@intel.com>,
        "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
        Konrad Rzeszutek Wilk <konrad@darnok.org>,
        David Miller <davem@davemloft.net>,
        Russell King <rmk@arm.linux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Chris Metcalf <cmetcalf@tilera.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Tony Luck <tony.luck@intel.com>, Paul Mundt <lethal@linux-sh.org>,
        Jeff Dike <jdike@addtoit.com>, Richard Weinberger <richard@nod.at>,
        Ralf Baechle <ralf@linux-mips.org>, Kyle McMartin <kyle@mcmartin.ca>,
        James Bottomley <jejb@parisc-linux.org>,
        Chris Zankel <chris@zankel.net>
Date: Thu, 28 Jun 2012 22:00:01 +1000
In-Reply-To: <1340881511.28750.19.camel@twins>
References: <20120627211540.459910855@chello.nl>
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	 <CA+55aFwa41fzvx8EZG_gODvw7hSpr+iP+w5fXp6jUcQh-4nFgQ@mail.gmail.com>
	 <1340838106.10063.85.camel@twins> <1340867364.20977.65.camel@pasglop>
	 <1340881511.28750.19.camel@twins>
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On Thu, 2012-06-28 at 13:05 +0200, Peter Zijlstra wrote:
> 
> > Some embedded ppc's know about the lowest level (SW loaded PMD) but
> > that's not an issue here. We flush these special TLB entries
> > specifically and synchronously in __pte_free_tlb().
> 
> OK, I missed that.. is that
> arch/powerpc/mm/tlb_nohash.c:tlb_flush_pgtable() ?

Yup.

> > > So even if the hardware did do speculative tlb fills, it would do
> them
> > > from the hash-table, but that's already cleared out.
> > 
> > Right,
> 
> Phew at least I got the important thing right ;-)

Yeah as long as we have that hash :-) The day we move on (if ever) it
will be as bad as ARM :-)

Cheers,
Ben.


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