From: Rik van Riel <riel@conectiva.com.br>
To: Martin Maletinsky <maletinsky@scs.ch>
Cc: linux-mm@kvack.org, kernelnewbies@nl.linux.org
Subject: Re: Question on pte bits
Date: Fri, 6 Dec 2002 14:08:17 -0200 (BRST) [thread overview]
Message-ID: <Pine.LNX.4.50L.0212061407120.22252-100000@duckman.distro.conectiva> (raw)
In-Reply-To: <3DF0BAD4.946B1845@scs.ch>
On Fri, 6 Dec 2002, Martin Maletinsky wrote:
> After getting the corresponding page table entry, the function makes a
> check, which I don't quite understand - if write access is requested to
> the page, it not only checks the write permission in the page table
> entry (with pte_write()), but also the dirty bit (with pte_dirty()). Why
> does a page need to be dirty in the case write == 1 (see line 444 in the
> code excerpt below?
If write == 1, then somebody wants to write to the page NOW.
In that case it's more efficient to just set the dirty bit
than to take a trap later on; remember that many CPUs can't
keep track of the dirty bit in hardware but trap to the OS.
Rik
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prev parent reply other threads:[~2002-12-06 16:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-12-06 14:57 Martin Maletinsky
2002-12-06 16:08 ` Rik van Riel [this message]
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