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Date:      Wed, 20 Feb 2008 13:01:18 -0800
From:      Alfred Perlstein <alfred@freebsd.org>
To:        Chuck Swiger <cswiger@mac.com>
Cc:        "freebsd-performance@freebsd.org" <freebsd-performance@freebsd.org>, Valerio Daelli <valerio.daelli@gmail.com>
Subject:   Re: Bad performance of 7.0 nfs client with Solaris nfs server
Message-ID:  <20080220210118.GY99258@elvis.mu.org>
In-Reply-To: <9BCE1D41-EC1A-4FE6-8551-E725DBE5D3A8@mac.com>
References:  <27dbfc8c0802190243y113d3059yd0c602850a4dbd6b@mail.gmail.com> <47BB33AD.1050005@FreeBSD.org> <27dbfc8c0802200323r13f69905l4940d0d5accd1eb1@mail.gmail.com> <9BCE1D41-EC1A-4FE6-8551-E725DBE5D3A8@mac.com>

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* Chuck Swiger <cswiger@mac.com> [080220 10:35] wrote:
> Hi--
> 
> On Feb 20, 2008, at 3:23 AM, Valerio Daelli wrote:
> >	99904 total packets received
> [ ... ]
> >
> >	61441 fragments received
> 
> [ ... ]
> >	34819 output datagrams fragmented
> >	208914 fragments created
> 
> Take a look at the level of packet fragmentation you are encountering;  
> yes, this is expected and things will work but there is extra latency  
> added when the IP stack has to reassemble packets before the data can  
> be delivered.  Try setting the NFS rsize/wsize to 1024 or perhaps 1400  
> and see whether that improves performance.
> 
> Or, if your switch and NICs support it, see whether you can get Gb  
> Ethernet jumbo frames working so that you don't have to fragment for  
> 2K or 4K data packets....

TCP mounts do not have this problem.  You can safely use
32k or higher sizes with TCP without fragmentation.

-Alfred



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