Re: VM/VFS bug with large amount of memory and file systems?

[Andrew Morton]

On Mon, 17 Sep 2007 16:46:47 -0400
Rik van Riel <riel@xxxxxxxxxx> wrote:

> Andrew Morton wrote:
> > On Mon, 17 Sep 2007 13:11:14 -0400
> > Rik van Riel <riel@xxxxxxxxxx> wrote:
> 
> >> IIRC I simply kept a list of all buffer heads and walked
> >> that to reclaim pages when the number of buffer heads is
> >> too high (and we need memory).  This list can be maintained
> >> in places where we already hold the lock for the buffer head
> >> freelist, so there should be no additional locking overhead
> >> (again, IIRC).
> > 
> > Christoph's slab defragmentation code should permit us to fix this:
> > grab a page of buffer_heads off the slab lists, trylock the page,
> > strip the buffer_heads.  I think that would be a better approach
> > if we can get it going because it's more general.
> 
> Is the slab defragmentation code in -mm or upstream already
> or can I find it on the mailing list?

Is on lkml and linux-mm: http://lkml.org/lkml/2007/8/31/329

> I've implemented code like you describe already, just give me
> a few days to become familiar with the slab defragmentation
> code and I'll get you a patch.

The patchset does buffer_heads: http://lkml.org/lkml/2007/8/31/348

I think the whole approach is reasonable.  It's mainly a matter of going
through it all with a toothcomb and getting it all merged up, tested and
integrated.  There's considerable potential for nasty and rarely-occurring
surprises in this stuff because it tends to approach locking in the
reversed order.

<checks the archives>

There were a few desultory comments, but I see no sign that the bulk of
the patches have had any serious review and testing from anyone yet.
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