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Date: Fri, 02 Jan 2009 12:39:43 -0600
From: Alan Cox <alc@cs.rice.edu>
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To: Mayur <mayur.shardul@gmail.com>
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Cc: Ed Schouten <ed@80386.nl>, Perforce Change Reviews <perforce@freebsd.org>,
	Mayur Shardul <mayur@freebsd.org>
Subject: Re: PERFORCE change 155554 for review
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Mayur wrote:
> Hi Ed,
> This work is not targeted to reduce the contention but this seems an 
> interesting problem. Will look in to it.
>

Have a look at pmap_enter() and pmap_remove_pages() and more generally 
the use of the page queues mutex to synchronize access to the per-page 
pv list in the pmap.  A simple and (likely) productive first step would 
be to introduce a new mutex in the pmap for synchronizing access to the 
per-page pv lists.

The tricky part is that the pmap functions sometimes manipulate other 
per-page fields, like "dirty", that are also synchronized by the page 
queues lock.

If you want to undertake this, I would be very supportive.

Regards,
Alan