Re: [PATCH v5 00/13] NFSD DIRECT and NFS DIRECT

[Mike Snitzer <snitzer@kernel.org>]

On Sun, Jul 27, 2025 at 11:39:18AM -0400, Chuck Lever wrote:
> On 7/24/25 3:30 PM, Mike Snitzer wrote:
> > Hi,
> > 
> > Some workloads benefit from NFSD avoiding the page cache, particularly
> > those with a working set that is significantly larger than available
> > system memory.  This patchset introduces _optional_ support to
> > configure the use of O_DIRECT or DONTCACHE for NFSD's READ and WRITE
> > support.  The NFSD default to use page cache is left unchanged.
> > 
> > The performance win associated with using NFSD DIRECT was previously
> > summarized here:
> > https://lore.kernel.org/linux-nfs/aEslwqa9iMeZjjlV@kernel.org/
> > This picture offers a nice summary of performance gains:
> > https://original.art/NFSD_direct_vs_buffered_IO.jpg
> > 
> > Similarly, NFS and LOCALIO in particular also benefit from avoiding
> > the page cache for workloads that have a working set that is
> > significantly larger than available system memory. Enter: NFS DIRECT,
> > which makes it possible to always enable LOCALIO to use O_DIRECT even
> > if the IO is not DIO-aligned.
> > 
> > For this v5 I've combined the NFSD and NFSD patchsets because the NFS
> > changes do depend on the the NFSD changes.  In addition, I think it
> > makes sense to review/test these changes together.
> 
> I'm ready to pull the six NFSD patches in this series into nfsd-testing.
> IMO we want regression and performance testing of NFSD, outside of the
> LOCALIO paths, before claiming merge readiness.

Makes sense, the NFSD changes are independent.  LOCALIO's access to
the dio alignment attrs in nfsd_file is a convenience.

Mike