What is the NFS max thread limit

[Rick Macklem]

Eric Browning wrote:
> I'm currently still debugging slow NFS performance on mac clients.
>  Running
> 9 stable with a mix of 200 Mac OS X 10.8, 10.7 and 10.6 clients.
> 
> Periodically I get this error on the mac side:
> automountd[1766]: set_and_fake_mapent_mntlevel: subdir=/Contents
> error:
> Contents not found in map=-fstab
> 
> I'm wondering with 200 clients with five nfsiod threads (~1000 nfsiod
> threads total) am I oversubscribing the nfs server?  I can't seem to
> configure any more than 256 threads (nfs_server_flags="-t -n 256").
>  When I
> configure above 256 I get an error about it resetting to 4:
> 
> Starting nfsd.
> nfsd: nfsd count 512; reset to 4
> 
> Tomorrow when all the mac clients have restarted I have changed their
> nfsiod threads down to 1 each to see if this is indeed the issue.
> 
Well, normally not all clients would be actively reading/writing files
concurrently, so I wouldn't expect your load to need more than 256 nfsd
threads. I also recall that you had a very large Access RPC load and
Access RPCs are not done by nfsiod threads. (nfsiod threads only do
readaheads and write behinds for buffer cache blocks of files.)

However, if you do want to try more than 256 nfsd threads, you will
need to edit nfsd.c and increase MAXNFSDCNT and then rebuild the nfsd
daemon from these modified sources.

I have no idea what causes the Mac OS X error, but you could try
posting on one of the Apple mailing lists like darwin-kernel at lists.apple.com.

rick
ps: The nfsd.c in head/current/10.0 also has a "--maxthreads" option
    that I don't think is limited to MAXNFSDCNT from a glance at the code.

> Thanks in advance,
> --
> Eric Browning
> Systems Administrator
> 801-984-7623
> 
> Skaggs Catholic Center
> Juan Diego Catholic High School
> Saint John the Baptist Middle
> Saint John the Baptist Elementary
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