Re: How to reclaim inode pages on demand

[Mel Gorman <mel@csn.ul.ie>]

On Wed, 10 Aug 2005, Andrew Morton wrote:

> Mel Gorman <mel@csn.ul.ie> wrote:
> >
> > On Mon, 8 Aug 2005, Andrew Morton wrote:
> >
> > > Mel Gorman <mel@csn.ul.ie> wrote:
> > > >
> > > > Hi,
> > > >
> > > > I am working on a direct reclaim strategy to free up large blocks of
> > > > contiguous pages. The part I have is working fine, but I am finding a
> > > > hundreds of pages that are being used for inodes that I need to reclaim. I
> > > > tried purging the inode lists using a variation of prune_icache() but it
> > > > is not working out.
> > > >
> > > > Given a struct page, that one knows is an inode, can anyone suggest the
> > > > best way to find the inode using it and free it?
> > >
> > > Simple answer: invalidate_mapping_pages(page->mapping, start, end).
> > >
> >
> > The majority of pages I am seeing no longer have page->mapping set. Does
> > this mean they are in the process of being cleared up?
>
> They're just anonymous pages, aren't they?  But you said "pages that are
> being used for inodes".  Confused.
>

So am I, I'm missing something really stupid.

What I have is the following;

1. Add a new flag GFP_INODE to mark inode pages
2. Add a GFP_INODE to the flags passed to mapping_set_gfp_mask() in
   fs/inode.c#alloc_inode(). This means that the page allocator will now
   know when it is allocating pages for inodes
3. Added a PG_inode flag for page->flags which will flag all pages that
   were allocated for inodes

(Note, I don't intend to use this flags in the long term, I've added them
for investigation purposes).

I later linearly scan the mem_map looking for pages that can be freed up
(usually LRU pages). I was expecting any page with PG_inode set to have a
page->mapping but not all of them do. It is the pages without a ->mapping
that are confusing the hell out of me.

-- 
Mel Gorman
Part-time Phd Student                          Java Applications Developer
University of Limerick                         IBM Dublin Software Lab
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