Document ways to reduce Copy times in the nfsd

[rmacklem]

Summary

For NFSv4.2, a Copy operation can take a long time to complete.
If there is a concurrent ExchangeID or DelegReturn operation
which requires the exclusive lock on all NFSv4 state, this can
result in a stall of the nfsd.

This patch documents ways to avoid this problem.

[• karels]

usr.sbin/nfsd/nfsd.8

363

This will produce "of the nfsd.", right? I think it would read better without "the", or maybe as "of the nfsd server".

[rmacklem]

This version has Mike Karel's suggested change.

[• karels]

usr.sbin/nfsd/nfsd.8

377

Minor: it might read better if "as a last resort" was first rather than last in this sentence. Sorry, should have noticed this earlier. I'll approve in any case.

[pauamma_gundo.com]

I'd move "as a last resort" to the head of the sentence as well, but that's fixable on commit.

[wollman]

Very minor comment: there should be markup for sysctl variables, but I haven't checked another manual page to be sure which one we're using. (My gut says .Li would be the expected formatting.)

[rmacklem]

In D44395#1012518, @wollman wrote:

Very minor comment: there should be markup for sysctl variables, but I haven't checked another manual page to be sure which one we're using. (My gut says .Li would be the expected formatting.)

It appears many use .Va so I have done that.

Thanks everyone for the review, rick