From owner-freebsd-current  Thu Nov 23 12:35:35 2000
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Date: Thu, 23 Nov 2000 14:35:30 -0600
From: Alan Cox <alc@cs.rice.edu>
To: Mike Smith <msmith@freebsd.org>,
	Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: current@freebsd.org
Subject: Re: page coloring
Message-ID: <20001123143530.E21300@cs.rice.edu>
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> Hi. 
> 
> Isn't the page coloring algoritm in _vm_page_list_find totally bogus?
> 

No, it's not.  The comment is, however, misplaced.  It describes
the behavior of an inline function in vm_page.h, and not the function
it precedes.

> It skips queue pq[index & PQ_L2_MASK].
> 

That's correct.  The inline function vm_page_list_find() in vm_page.h
has already failed to allocate a page of the desired color, index,
and so _vm_page_list_find() is called to allocate a page of ANY other
color it can find.

Rather than choose a random page, the odd-looking loop in
_vm_page_list_find() tries to find a page whose color is unlikely
to equal the neighboring pages in the vm object if colored allocation
for them succeeded.

Alan


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