Re: [RFC] Early flush (was: spindown)

[Daniel Phillips <phillips@bonn-fries.net>]

On Sunday 24 June 2001 17:06, Rik van Riel wrote:
> On Sun, 24 Jun 2001, Anuradha Ratnaweera wrote:
> > It is not uncommon to have a large number of tmp files on the disk(s)
> > (Rik also pointed this out somewhere early in the original thread) and
> > it is sensible to keep all of them in buffers if RAM is sufficient.
> > Transfering _very_ large files is not _that_ common so why shouldn't
> > that case be handled from the user space by calling sync(2)?
>
> Wait a moment.
>
> The only observed bad case I've heard about here is
> that of large files being written out.

But that's not the only advantage of doing the early update:

  - Early spindown for laptops
  - Improved latency under some conditions
  - Improved throughput for some loads
  - Improved filesystem safety

> It should be easy enough to just trigger writeout of
> pages of an inode once that inode has more than a
> certain amount of dirty pages in RAM ... say, something
> like freepages.high ?

The inode dirty page list is not sorted by "time dirtied" so you would be 
eroding the system's ability to ensure that dirty file buffers never get 
older than X.

--
Daniel