> On Aug 10, 2020, at 3:07 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > Thanks for the test results: > > On Mon, Aug 10, 2020 at 02:21:34PM -0400, Chuck Lever wrote: >> For these results I've switched to sec=sys so the test completes faster. >> >> NFSv3/sys: 953.37user 5101.96system 14:13.78elapsed 709%CPU (0avgtext+0avgdata 107160maxresident)k >> >> NFSv4.1/sys: 953.64user 5202.27system 17:54.51elapsed 572%CPU (0avgtext+0avgdata 107204maxresident)k >> >> NFSv4.0/sys unpatched: 965.44user 5406.75system 36:10.72elapsed 293%CPU (0avgtext+0avgdata 107252maxresident)k >> >> NFSv4.0/sys with fix: 968.38user 5359.18system 30:50.38elapsed 341%CPU (0avgtext+0avgdata 107140maxresident)k > > Well, that didn't work! > > So maybe it's write opens that are the problem in this case. The below > should mostly revert to pre-94415b06eb8a behavior in the 4.0 case, so if > this doesn't fix it then I was wrong about the cause.... > > --b. > > commit 0e94ee0b6f11 > Author: J. Bruce Fields <bfields@xxxxxxxxxx> > Date: Sun Aug 9 17:11:59 2020 -0400 > > nfsd4: don't grant delegations on 4.0 create opens > > Chuck reported a major slowdown running the git regression suite over > NFSv4.0. > > In the 4.0 case, the server has no way to identify which client most > metadata-modifying operations come from. So, for example, the common > pattern of an create or write open followed by a setattr is likely to > result in an immediate break in the 4.0 case. > > It's probably not worth giving out delegations on 4.0 write or create > opens. > > Reported-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index fdba971d06c3..0d51d1751592 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -5096,6 +5096,19 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, > goto out_no_deleg; > if (!cb_up || !(oo->oo_flags & NFS4_OO_CONFIRMED)) > goto out_no_deleg; > + if (clp->cl_minorversion) > + break; > + /* > + * In the absence of sessions, most operations > + * that modify metadata (like setattr) can't > + * be linked to the client sending them, so > + * will result in a delegation break. That's > + * especially likely for write and create opens: > + */ > + if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) > + goto out_no_deleg; > + if (open->op_create == NFS4_OPEN_CREATE) > + goto out_no_deleg; > break; > default: > goto out_no_deleg; Roughly the same result with this patch as with the first one. The first one is a little better. Plus, I think the Solaris NFS server hands out write delegations on v4.0, and I haven't heard of a significant issue there. It's heuristics may be different, though. So, it might be that NFSv4.0 has always run significantly slower. I will have to try a v5.4 or older server to see. Also, instead of timing, I should count forward channel RPCs and callbacks, or perhaps the number of DELAY responses. Don't touch that dial! -- Chuck Lever
