Re: [resent PATCH] Re: very slow parallel read performance

Rik van Riel
2001-08-27T15:15:37Z

On Mon, 27 Aug 2001, Alex Bligh - linux-kernel wrote:

> A nit: I think it's a MRU list you want.

Absolutely, however ...

> If you are reading
> ahead (let's have caps for a page that has been used for reading,
> as well as read from the disk, and lowercase for read-ahead that
> has not been used):
> ABCDefghijklmnopq
> | |
> read disk
> ptr head
> and you want to reclaim memory, you want to drop (say) 'pq'
> to get
> ABCDefghijklmno
> for two reasons: firstly because 'efg' etc. are most likely
> to be used NEXT, and secondly because the diskhead is nearer
> 'pq' when you (inevitably) have to read it again.

This is NOT MRU, since p and q have not been used yet.
In this example you really want to drop D and C instead.

regards,

Rik
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