Subject: Re: [patch 3/9] Guest page hinting: volatile page cache.
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reply-To: schwidefsky@de.ibm.com
To: Dave Hansen <haveblue@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>, linux-kernel@vger.kernel.org,
       virtualization@lists.osdl.org, akpm@osdl.org, nickpiggin@yahoo.com.au,
       frankeh@watson.ibm.com
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Organization: IBM Corporation
Date: Fri, 01 Sep 2006 20:31:44 +0200
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On Fri, 2006-09-01 at 11:23 -0700, Dave Hansen wrote:
> OK, and there's no other workable solution to exclude each other from
> running at the same time than a bit in page->flags?
> 
> It seems like that hashed lock (or lock in mem_map[]) we were talking
> about earlier might be applicable here, too.

The indication which page has already been removed from the page cache
by a discard fault is by definition per-page. The situation is different
compared to the one with PG_state_change which is used to protect
critical sections. After the cpu left the critical section the bit can
be clear again. The discard bit cannot be cleared until the page really
has been freed.

-- 
blue skies,
  Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.


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