Subject: Re: /etc/mtab read ~900 times by rpc.mountd
To: linux-nfs@vger.kernel.org
References: <f9dcc371-cd94-6b39-dd6a-b412bdf03df4@cs.uchicago.edu>
 <8737a9x9ky.fsf@notabene.neil.brown.name> <595F1A3A.7070405@cs.uchicago.edu>
 <87efto69rs.fsf@notabene.neil.brown.name>
 <4ec2a8fc-3ca5-d26b-7742-be4e2f749c21@cs.uchicago.edu>
 <87y3rv4zrb.fsf@notabene.neil.brown.name>
 <1740081e-6180-1c88-0a0c-8747a92c65a1@cs.uchicago.edu>
 <87bmoq4h41.fsf@notabene.neil.brown.name>
From: Phil Kauffman <kauffman@cs.uchicago.edu>
Message-ID: <9e16d6c3-a675-b53e-c6f3-dfa9cdf1d5c9@cs.uchicago.edu>
Date: Wed, 12 Jul 2017 12:55:38 -0500
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On 07/11/2017 07:46 PM, NeilBrown wrote:
> So the new data shows about 7 seconds for a login, which is probably
> a little longer than you would like, but might be acceptable?
Unfortunately, the delay is not acceptable.

The ideal would be to achieve performance parity with when one is not 
forced to use the 'crossmnt' option.

My current setup (home directory server) does not require 'crossmnt' and 
does not incur a delay. It is a standard nfs server using mdadm, lvm, 
and xfs.

While my current setup is probably "normal" and using nested datasets 
with the 'crossmnt' option might be "weird" now; nested mounts will 
probably only become more common as BTRFS, ZFS, and other filesystems 
with similar features gain traction on linux.


> That is more than a 2-line patch.  I might have a go later this week.
That would be super! Thanks for taking a look.


-- 
Phil Kauffman
Systems Admin
Dept. of Computer Science
University of Chicago
kauffman@cs.uchicago.edu