On Sat, Jan 13, 2024 at 2:32 AM Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Sat, 2024-01-13 at 01:19 +0100, Dan Shelton wrote: > > We've been experiencing significant nfsd performance problems with a > > customer who has a deeply nested filesystem hierarchy, lots of > > subdirs, some of them 60-80 dirs deep (!!), which leads to an > > exponentially slowdown with nfsd accesses. > > > > Some of the issues have been addressed by implementing a better > > directory walker via multiple dir fds and openat() (instead of just > > cwd+open()), but the nfsd side still was a pretty dramatic issue, > > until we bumped #define NFSD_MAX_OPS_PER_COMPOUND in > > linux-6.7/fs/nfsd/nfsd.h from 50 to 96. After that the nfsd side > > behaved MUCH more performant. > > I guess your clients are trying to do a long pathwalk in a single > COMPOUND? Is there a problem with that (assuming NFSv4.1 session limits are honored) ? > Is this the windows client? No, the ms-nfs41-client (see https://github.com/kofemann/ms-nfs41-client) uses a limit of |16|, but it is on our ToDo list to bump that to |128| (but honoring the limit set by the NFSv4.1 server during session negotiation) since it now supports very long paths ([1]) and this issue is a known performance bottleneck. [1]=Windows 10 build 1607 allows longer paths than the infamous |MAXPATH|, see https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=registry > At first glance, I don't see any real downside to increasing that value. > Maybe we can bump it to 100 or so? What would probably be best is to > propose a patch so we can discuss the change formally. AFAIK the Solaris 11's and Illumos's (see https://github.com/racktopsystems/illumos-gate/commit/27e4199512d9d7b1e5409904f13cd96d8a05ee6e) limit is AFAIK |NFS4_COMPOUND_LIMIT| (=|2048|), both capped by the limits negotiated at NFSv4.1 session creation, if I recall it correctly... ---- Bye, Roland -- __ . . __ (o.\ \/ /.o) roland.mainz@xxxxxxxxxxx \__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer /O /==\ O\ TEL +49 641 3992797 (;O/ \/ \O;)
