Re: [PATCH v7 05/14] NFSD: @stable for direct writes is always NFS_FILE_SYNC

[Mike Snitzer <snitzer@kernel.org>]

On Mon, Oct 27, 2025 at 11:04:47AM -0400, Chuck Lever wrote:
> On 10/27/25 10:58 AM, Mike Snitzer wrote:
> >>> The current approach of using IOCB_DSYNC|IOCB_SYNC have performed
> >>> really well on modern NVMe servers.
> >> NVMe does not implement a concept called servers.
> > But you're aware that servers have NVMe devices in them.. that's all I
> > meant.  All of these NFSD_IO_DIRECT changes have been developed and
> > tested in modern servers with 8 NVMe, see:
> > https://www.youtube.com/watch?v=tpPFDu9Nuuw
> > 
> > (NOTE: results covered in this session did _not_ have the benefit
> > of NFSD responding to client with NFS_FILE_SYNC to avoid COMMIT, the
> > ability to do so was discussed at Bakeathon and was acted on with
> > these latest NFSD Direct patchsets).
> 
> This is why I suspect that leaving direct writes as UNSTABLE, rather
> than promoting them to FILE_SYNC, is probably not going to make much
> difference to Jonathan's benchmark results. That's just a guess though.
> 
> IOW the memory costs of sticking with UNSTABLE + COMMIT have already
> been demonstrated, and it's low.
> 
> The v8 of this series will go back to that idea, and if you want, you
> can benchmark it again. If it regresses, we can stick with FILE_SYNC.
> It's just ones and zeroes, as they say.

OK.