an easy (?) question on namecache sizing

[Kirk McKusick]

> Date: Thu, 5 Nov 2015 22:52:55 +0200
> From: Konstantin Belousov <kostikbel at gmail.com>
> To: Kirk McKusick <mckusick at mckusick.com>
> Subject: Re: an easy (?) question on namecache sizing
> Cc: fs at freebsd.org
> 
> On Thu, Nov 05, 2015 at 12:25:38PM -0800, Kirk McKusick wrote:
>> 
>> Does moving the setting of wantfreevnodes before the cache size changes
>> (as redone above) close the window enough? The vlrureclaim() function
>> operates slowly enough that a brief period of inconsistency seems
>> unimportant. Changing desiredvnodes happens very rarely. And at the moment
>> we are not correcting wantfreevnodes at all. Or am I missing some key point?
> 
> I think wantfreevnodes should be set before the cache size changes when
> desiredvnodes is decreased, but kept at the place in your patch for the
> increasing case.

What is the benefit of waiting until after the caches are resized
for setting wantfreevnodes when desiredvnodes is increasing? It
seems like it just complicates the code to conditionally do the
update in two places, so I am inclined to just do it at the beginning
as there is good reason for doing it there when downsizing and for
the upsizing it does not really matter much.

	Kirk McKusick