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

From: Christoph Lameter
Date: Thu Apr 19 2007 - 21:16:18 EST


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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