Re: alloc_pages_bulk()

[Jesper Dangaard Brouer <brouer@redhat.com>]

On Mon, 8 Feb 2021 17:50:51 +0000
Chuck Lever <chuck.lever@oracle.com> wrote:

> Sorry for resending. I misremembered the linux-mm address.
> 
> > Begin forwarded message:
> > 
> > [ please Cc: me, I'm not subscribed to linux-mm ]
> > 
> > We've been discussing how NFSD can more efficiently refill its
> > receive buffers (currently alloc_page() in a loop; see
> > net/sunrpc/svc_xprt.c::svc_alloc_arg()).
> > 

It looks like you could also take advantage of bulk free in:
 svc_free_res_pages()

I would like to use the page bulk alloc API here:
 https://github.com/torvalds/linux/blob/master/net/core/page_pool.c#L201-L209


> > Neil Brown pointed me to this old thread:
> > 
> > https://lore.kernel.org/lkml/20170109163518.6001-1-mgorman@techsingularity.net/
> > 
> > We see that many of the prerequisites are in v5.11-rc, but
> > alloc_page_bulk() is not. I tried forward-porting 4/4 in that
> > series, but enough internal APIs have changed since 2017 that
> > the patch does not come close to applying and compiling.

I forgot that this was never merged.  It is sad as Mel showed huge
improvement with his work.

> > I'm wondering:
> > 
> > a) is there a newer version of that work?
> > 

Mel, why was this work never merged upstream?


> > b) if not, does there exist a preferred API in 5.11 for bulk
> > page allocation?
> > 
> > Many thanks for any guidance!

I have a kernel module that micro-bench the API alloc_pages_bulk() here:
 https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/bench/page_bench04_bulk.c#L97

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer