Re: [PATCH v2 net-next 3/4] net: introduce common dev_page_is_reserved()

[Alexander Lobakin]

From: Jakub Kicinski <kuba@xxxxxxxxxx>
Date: Sat, 30 Jan 2021 11:07:07 -0800

> On Sat, 30 Jan 2021 15:42:29 +0000 Alexander Lobakin wrote:
> > > On Wed, 27 Jan 2021 20:11:23 +0000 Alexander Lobakin wrote:
> > > > + * dev_page_is_reserved - 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 true if this page should be returned to page allocator, false
> > > > + * otherwise.
> > > > + */
> > > > +static inline bool dev_page_is_reserved(const struct page *page)
> > >
> > > Am I the only one who feels like "reusable" is a better term than
> > > "reserved".
> >
> > I thought about it, but this will need to inverse the conditions in
> > most of the drivers. I decided to keep it as it is.
> > I can redo if "reusable" is preferred.
> 
> Naming is hard. As long as the condition is not a double negative it
> reads fine to me, but that's probably personal preference.
> The thing that doesn't sit well is the fact that there is nothing
> "reserved" about a page from another NUMA node.. But again, if nobody
> +1s this it's whatever...

Agree on NUMA and naming. I'm a bit surprised that 95% of drivers
have this helper called "reserved" (one of the reasons why I finished
with this variant).
Let's say, if anybody else will vote for "reusable", I'll pick it for
v3.

> That said can we move the likely()/unlikely() into the helper itself?
> People on the internet may say otherwise but according to my tests
> using __builtin_expect() on a return value of a static inline helper
> works just fine.

Sounds fine, this will make code more elegant. Will publish v3 soon.

Thanks,
Al