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From: Ingo Molnar <mingo@elte.hu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Cree <mcree@orcon.net.nz>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch@vger.kernel.org, David Miller <davem@davemloft.net>,
	Russell King <rmk@arm.linux.org.uk>
Subject: Re: Software prefetching considered harmful
Date: Sat, 21 May 2011 12:42:09 +0200	[thread overview]
Message-ID: <20110521104209.GB26447@elte.hu> (raw)
In-Reply-To: <1305951535.7481.198.camel@pasglop>


* Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Sat, 2011-05-21 at 15:37 +1200, Michael Cree wrote:
> > While this is not a concern to the kernel (it obviously has access to
> > location 0) 
> 
> Not that obvious... dunno how you do your memory map on alpha but on
> most architectures, 0 is userspace even when you're in the kernel and is
> typically not mapped.

Correct, it's like that on x86 as well.

Filtering out NULLs in the prefetch primitives or making sure NULL never gets 
prefetched looks like to be a generally good idea.

Thanks,

	Ingo

  reply	other threads:[~2011-05-21 10:42 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-19 17:12 Software prefetching considered harmful Linus Torvalds
2011-05-19 19:05 ` Linus Torvalds
2011-05-19 19:28   ` Ingo Molnar
2011-05-21  3:37     ` Michael Cree
2011-05-21  4:18       ` Benjamin Herrenschmidt
2011-05-21 10:42         ` Ingo Molnar [this message]
2011-05-19 19:32   ` David Miller
2011-05-19 19:38     ` Linus Torvalds
2011-05-19 19:47       ` David Miller
2011-05-19 23:34         ` Ingo Molnar
2011-05-20 16:01           ` Catalin Marinas
2011-05-20  1:42   ` Benjamin Herrenschmidt
2011-05-20  8:34     ` Ingo Molnar
2011-05-20  9:13       ` Benjamin Herrenschmidt

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