linux-kernel - Re: [RFC 0/8] Variable Order Page Cache

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Message-ID: <Pine.LNX.4.64.0704191815180.14874@schroedinger.engr.sgi.com>
Date:	Thu, 19 Apr 2007 18:15:53 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Maxim Levitsky <maximlevitsky@...il.com>
cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Paul Jackson <pj@....com>, Dave Chinner <dgc@....com>,
	Andi Kleen <ak@...e.de>
Subject: Re: [RFC 0/8] Variable Order Page Cache

On Fri, 20 Apr 2007, Maxim Levitsky wrote:

> First of all, today, packet writing on cd/dvd doesn't work well, it is very 
> slow because 
> now all file-systems are limited to 4k-barrier and cd/dvd can write only 
> 32k/64k packets.
> This is why a pktcdvd was written and it emulates those 4k sectors by doing 
> read/modify/write cycle
> This cause a lot of seeks and read/writing switches and thus it is very slow.
> 
> By introducing a bigger that 4k page cache a dvd/cd can be divided is 64k/32k 
> blocks that will be read an written freely
> (Although dvd can read 2k  I don't think that reading a 64k block will hurt 
> since most of time drive is busy seeking and locating a specific sector)
> 
> Now I thinking to implement this in an other way, I mean I want to teach udf 
> filesystem to to packet writing on its own, bypassing disk cache (but not page 
> cache)
> 
> Secondary 32/64k limitation is present of flash devices too, so they can 
> benefit too, and I almost sure that future hard disks will use bigger block 
> size too.
> 
> To summarize I want to tell that bigger pagesize will allow devices that have 
> big hardware sectors to work fine in linux.

Great arguments in support of this feature. Thank you.

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