Re: journaling & VM (was: Re: reiserfs being part of the kernel:it'snot just the code)

[Chris Mason <mason@suse.com>]

On Wed, 7 Jun 2000, Stephen C. Tweedie wrote:

> Hi,
> 
> On Tue, Jun 06, 2000 at 08:45:08PM -0700, Hans Reiser wrote:
> > > 
> > > This is the reason because of what I think that one operation in the
> > > address space makes no sense.  No sense because it can't be called
> > > from the page.
> > 
> > What do you think of my argument that each of the subcaches should register
> > currently_consuming counters which are the number of pages that subcache
> > currently takes up in memory,
> 
> There is no need for subcaches at all if all of the pages can be
> represented on the page cache LRU lists.  That would certainly make
> balancing between caches easier.  However, there may be caches which
> don't fit that model --- how would it work for ReiserFS if the cache 
> balancing was all done through the page cache?  

Right now, almost of the pinned pages will be buffer cache pages, and only
metadata is logged.  But, sometimes a data block must be flushed before
transaction commit, and those pages are pinned, but can be written at any
time.  I'm not sure I fully understand the issues with doing all the
balancing through the page cache...

Allocate on flush will be different, and the address_space->pressure()
method makes even more sense there.  Those pages will be on the LRU lists,
and you want the pressure function to be called on each page.

-chris

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