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Date: Fri, 25 Nov 2016 15:57:25 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Rick Macklem <rmacklem@uoguelph.ca>
Cc: Alan Somers <asomers@freebsd.org>,
 FreeBSD CURRENT <freebsd-current@freebsd.org>
Subject: Re: NFSv4 performance degradation with 12.0-CURRENT client
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On Fri, Nov 25, 2016 at 12:54:07PM +0000, Rick Macklem wrote:
> Well, ideally theer would be a VOP_MMAPDONE() or something like that, which
> would tell the NFSv4 client that I/O is done on the vnode so it can close it.
> If there was some way for the NFSv4 VOP_CLOSE() to be able to tell if the file
> has been mmap'd, that would help since it could close the ones that are not
> mmap'd on the last descriptor close.
> (A counter wouldn't be as useful, since NFSv4 would have to keep checking it to
>  see if it can do the close yet, but it might still be doable.)

I thought that the issue was in tracking any opens and mmaps, but from this
reply it is not that clear.  Do you need callback when all opens and mmaps
have ended, or only opens and mmaps for write ?  If later, we already have
a suitable mechanism VOP_ADD_WRITECOUNT().