Re: Review of Thomas's >2GB ext2fs proposal

[Neal H. Walfield]

> > The hashes and an array consisting of the reference count, a bit
> > indicating if the page is in the kernel and another bit indicating if
> > the page is allocated.
> 
> I could perfectly well adopt exactly the same strategy, and use a
> cheaper but less precise policy for dropping cached mappings, if there
> is really concern about the memory consumption of two extra pointers
> per mapping.
> 
> Because mappings are cheaper, it is much less important to have
> excellent long-term behavior.  It is really the near-term things that
> are important; the many successive operations on the same inode, for
> example.  In such a case, it is very unlikely that the drop random
> mapping strategy will drop something actually in active use.

I am interested in the following detail of your plan: when do you
drain the cache?  When it is full?  If we set the cache size to 2GB
then you have a lot of mappings to manage.  The hashes that I have are
proportional to the size of the kernel cache.

Neal