On Wed, Apr 23, 2025 at 10:38:37AM -0400, Chuck Lever wrote: > On 4/23/25 12:25 AM, trondmy@xxxxxxxxxx wrote: > > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > > > The following patch set attempts to add support for the RWF_DONTCACHE > > flag in preadv2() and pwritev2() on NFS filesystems. > > Hi Trond- > > "RFC" in the subject field noted. > > The cover letter does not explain why one would want this facility, nor > does it quantify the performance implications. > > I can understand not wanting to cache on an NFS server, but don't you > want to maintain a data cache as close to applications as possible? If you look at the original work for RWF_DONTCACHE, you'll see this is the application providing the hint that it's doing a streaming access. It's only applied to folios which are created as a result of this access, and other accesses to these folios while the folios are in use clear the flag. So it's kind of like O_DIRECT access, except that it does go through the page cache so there's none of this funky alignment requirement on the userspace buffers.
