From: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Date: Sun, 31 Jan 2021 12:22:05 +0000
> On Sun, Jan 31, 2021 at 12:11:52PM +0000, Alexander Lobakin wrote:
> > A bunch of drivers test the page before reusing/recycling for two
> > common conditions:
> > - if a page was allocated under memory pressure (pfmemalloc page);
> > - if a page was allocated at a distant memory node (to exclude
> > slowdowns).
> >
> > Introduce a new common inline for doing this, with likely() already
> > folded inside to make driver code a bit simpler.
>
> I don't see the need for the 'dev_' prefix. That actually confuses me
> because it makes me think this is tied to ZONE_DEVICE or some such.
Several functions right above this one also use 'dev_' prefix. It's
a rather old mark that it's about network devices.
> So how about calling it just 'page_is_reusable' and putting it in mm.h
> with page_is_pfmemalloc() and making the comment a little less network-centric?
This pair of conditions (!pfmemalloc + local memory node) is really
specific to network drivers. I didn't see any other instances of such
tests, so I don't see a reason to place it in a more common mm.h.
> Or call it something like skb_page_is_recyclable() since it's only used
> by networking today. But I bet it could/should be used more widely.
There's nothing about skb. Tested page is just a memory chunk for DMA
transaction. It can be used as skb head/frag, for XDP buffer/frame or
for XSK umem.
> > +/**
> > + * dev_page_is_reusable - check whether a page can be reused for network Rx
> > + * @page: the page to test
> > + *
> > + * A page shouldn't be considered for reusing/recycling if it was allocated
> > + * under memory pressure or at a distant memory node.
> > + *
> > + * Returns false if this page should be returned to page allocator, true
> > + * otherwise.
> > + */
> > +static inline bool dev_page_is_reusable(const struct page *page)
> > +{
> > + return likely(page_to_nid(page) == numa_mem_id() &&
> > + !page_is_pfmemalloc(page));
> > +}
> > +
Al
