> On Wed, 17 Jan 2007 11:43:42 -0800 (PST) Christoph Lameter <[email protected]> wrote:
> On Tue, 16 Jan 2007, Andrew Morton wrote:
>
> > Do what blockdevs do: limit the number of in-flight requests (Peter's
> > recent patch seems to be doing that for us) (perhaps only when PF_MEMALLOC
> > is in effect, to keep Trond happy) and implement a mempool for the NFS
> > request critical store. Additionally:
> >
> > - we might need to twiddle the NFS gfp_flags so it doesn't call the
> > oom-killer on failure: just return NULL.
> >
> > - consider going off-cpuset for critical allocations. It's better than
> > going oom. A suitable implementation might be to ignore the caller's
> > cpuset if PF_MEMALLOC. Maybe put a WARN_ON_ONCE in there: we prefer that
> > it not happen and we want to know when it does.
>
> Given the intermediate layers (network, additional gizmos (ip over xxx)
> and the network cards) that will not be easy.
Paul has observed that it's already done. But it seems to not be working.
> > btw, regarding the per-address_space node mask: I think we should free it
> > when the inode is clean (!mapping_tagged(PAGECACHE_TAG_DIRTY)). Chances
> > are, the inode will be dirty for 30 seconds and in-core for hours. We
> > might as well steal its nodemask storage and give it to the next file which
> > gets written to. A suitable place to do all this is in
> > __mark_inode_dirty(I_DIRTY_PAGES), using inode_lock to protect
> > address_space.dirty_page_nodemask.
>
> The inode lock is not taken when the page is dirtied.
The inode_lock is taken when the address_space's first page is dirtied. It is
also taken when the address_space's last dirty page is cleaned. So the place
where the inode is added to and removed from sb->s_dirty is, I think, exactly
the place where we want to attach and detach address_space.dirty_page_nodemask.
> The tree_lock
> is already taken when the mapping is dirtied and so I used that to
> avoid races adding and removing pointers to nodemasks from the address
> space.
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