Re: [PATCH 18/18] xfs: stop using the page cache to back the buffer cache

Dave Chinner
2010-09-15T00:06:08Z

On Tue, Sep 14, 2010 at 07:20:04PM -0400, Christoph Hellwig wrote:
> On Tue, Sep 14, 2010 at 08:56:17PM +1000, Dave Chinner wrote:
> > The only open question is how to best handle sub-page buffers - can we use
> > kmalloc/slab memory for sub-page sized buffers, or do we need to split up
> > pages ourselves? Worth noting is that the current code still works on sub-page
> > block size filesystems, it is just inefficient w.r.t. memory usage.
>
> As mentioned before I think we're fine to use slab/kmalloc pages now.
> In fact using them will probably be more efficient than the current
> code, given that at least btree blocks usually won't be close to each
> other, so the old code wasted lots of memory for it, too.

Good point. I'll start working on this later today.

>
> > for (i = 0; i < bp->b_page_count; i++) {
> > struct page *page;
> > uint retries = 0;
> > +retry:
> > + page = alloc_page(gfp_mask);
> > if (unlikely(page == NULL)) {
> > if (flags & XBF_READ_AHEAD) {
> > bp->b_page_count = i;
> > for (i = 0; i < bp->b_page_count; i++)
> > + __free_page(bp->b_pages[i]);
> > return -ENOMEM;
>
> Maybe convert this to and out_free_pages goto while you're at it?

Yes, sounds reasonable. Will do.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com