Re: Delaying writes to disk when there's no need

[John Bradford]

> If the memory does get written to again before the writeout timeout
> then yeah its used some cpu, memory, pci, etc that it didn't have
> to.

It will presumably also have filled the cache with the writeout data.

> > Ultimately its all a tradeoff.  Do you write now, or do you hold off 
> > and hope that you can throw away some of the writes because new stuff 
> > will home in to overwrite them?
> 
> Yes it is a tradeoff. Having an idle disk gives more weight to "write now".

Not necessarily.  What if you are using a solid state disk which only
allows a relatively low number of re-write cycles?  What if the disk
is spun down, and spinning it up uses a lot of power?  On a laptop,
you don't necessarily want the disk spinning up just to write one
sector.

John.