Re: Comparing buffer cache algorithms on 2.2.17. Suggestions?

[Stephen Tweedie <sct@redhat.com>]

Hi,

On Sat, Feb 17, 2001 at 02:15:40PM -0800, Fireball Freddy wrote:
> 
>   o Eliminate BUF_CLEAN, BUF_DIRTY, and BUF_LOCKED
> lists in favor of a single BUF_LRU list.  This because
> I don't see the point of maintaining three lists...
> the only time I need to find all the dirty blocks is
> on a sync of some sort.  I don't mind if the sync
> takes a while longer if the normal operating condition
> is faster.

What if you have a gig of buffer cache in the system?  You still need
to maintain the single LRU, so you're not going to be saving that much
on the main codepaths, and walking a gig of unnecessary buffer_heads
every kupdate() flush is not going to be cheap.

>   It looks like the ext2 fs is going to complicate
> this somewhat, as it sets blocks dirty and/or writes
> them itself sometimes.  Not sure how I'm going to get
> around this... will probably ignore it for now.

Yep, this behaviour on the superblock and group descriptors has hurt
people in the past.

Cheers,
 Stephen