From owner-freebsd-hackers  Mon Aug 17 16:44:06 1998
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To: zhihuizhang <bf20761@binghamton.edu>
cc: hackers <freebsd-hackers@FreeBSD.ORG>
Subject: Re: Virtual Memory for buffer 
In-reply-to: Your message of "Mon, 17 Aug 1998 16:42:37 EDT."
             <Pine.SOL.L3.93.980817163010.19727B-100000@bingsun2> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Mon, 17 Aug 1998 16:42:53 -0700
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>The virtual memory of buffer is allocated from buffer_map in getnewbuf() 
>by calling vm_map_findspace() and vm_map_insert(). Its address is saved in
>b_kvasize and (sometimes) b_data.  These are fine.  However, when
>allocbuf() extend VMIO buffer size, it *truncates* b_data to a page
>boundary before entering buffer pages into KVA.
>
>I wonder if virtual address space is not always allocated on page
>boundary, then it is possible that after the PTE has changed to point to

   Space is always allocated on a page boundry.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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