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Date:      Sun, 19 Sep 1999 21:07:00 +0200
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Matthew Jacob <mjacob@feral.com>, dg@root.com, Greg Lehey <grog@lemis.com>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG
Subject:   Re: User block device access 
Message-ID:  <17519.937768020@critter.freebsd.dk>
In-Reply-To: Your message of "Sun, 19 Sep 1999 12:00:26 PDT." <199909191900.MAA73792@apollo.backplane.com> 

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In message <199909191900.MAA73792@apollo.backplane.com>, Matthew Dillon writes:

>    In fact, a memory-mappable buffered block device with write-through would
>    be much, much more useful to a database then a character device, and I 
>    think it's only a two line patch to make mmap() work, and probably a 
>    four line patch to implement write-through.  It would be virtually
>    unbeatable... use of mmap() removes the extra copy overhead, read-caching
>    takes the burden off the application, optional write-through gives you 
>    instant feedback *AND* reblocking.  I would even be willing to make the
>    write-through the default.
>
>    That would give us an extremely powerful and useful buffered block device
>    implementation.

Now that is the kind of attitude I like to work with: constructive and
full of good ideas.  Thankyou Matt!

So you are saying that we could basically leave read/write as they
are for cdevs and provide the buffer/cache mechanisms with mmap ?

--
Poul-Henning Kamp             FreeBSD coreteam member
phk@FreeBSD.ORG               "Real hackers run -current on their laptop."
FreeBSD -- It will take a long time before progress goes too far!


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