On Sat, 2025-03-08 at 15:14 -0500, cel@xxxxxxxxxx wrote: > From: Chuck Lever <chuck.lever@xxxxxxxxxx> > > The usual policy for kernel-user space APIs is that once a public > API appears, it is difficult to change or remove, in order to > maintain backwards compatibility with user space software. > > This series introduces /sys/kernel/debug/nfsd/ where we can > hopefully place ephemeral and undocumented settings for testing NFSD > features that are to be added or deprecated without the worry of > having to support an administrative API forever without change, > amen. > > As a first consumer of this user-kernel API, the series adds a > simple disable-splice-read setting, which can force all NFS READ > operations to use vfs_iter_read() rather than page splicing to fill > data content for an NFS reply. > > The splice read path is the default on most file systems, so it gets > most of the test experience. The purpose of this new setting is to > enable test runners to force the use of the iov iter path. We are > also interested in comparing the performance of the splice and iter > paths, as a prelude to potentially removing page splicing. This new > setting makes it easy to benchmark either read mode without having > to rebuild the kernel. > > We have an eye on a few other consumers, such as uncached I/O and > increasing the maximum r/wsize, for which /sys/kernel/debug/nfsd > might be suitable while their performance impact is studied before > a concrete administrative interface is agreed upon. > > Opinions and code review are welcome, as always. > > Chuck Lever (2): > NFSD: Add /sys/kernel/debug/nfsd > NFSD: Add experimental setting to disable the use of splice read > > fs/nfsd/Makefile | 1 + > fs/nfsd/debugfs.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsctl.c | 4 ++++ > fs/nfsd/nfsd.h | 10 ++++++++++ > fs/nfsd/vfs.c | 4 ++++ > 5 files changed, 66 insertions(+) > create mode 100644 fs/nfsd/debugfs.c > Looks good to me: Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
