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From: John Baldwin <jhb@freebsd.org>
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Subject: Re: ixgbe/NFS m_defrag() instrumentation
Date: Tue, 11 Feb 2014 13:58:54 -0500
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 (bigwig.baldwin.cx); Tue, 11 Feb 2014 14:49:54 -0500 (EST)
Cc: rmacklem@freebsd.org, Garrett Wollman <wollman@freebsd.org>
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On Wednesday, February 05, 2014 12:27:15 am Garrett Wollman wrote:
> I instrumented calls to m_defrag() in ixgbe.  As expected, it gets
> called *a lot* when NFS is running with the default read size of 64k.
> A simple benchmark (single-threaded sequential read of a 128 GB file
> which I didn't even run to completion) tells the tale:
> 
> $ sysctl dev.ix.0.mbuf_defrag_attempted
> dev.ix.0.mbuf_defrag_attempted: 1737994
> 
> (There's already a similar counter for m_defrag() failures, which made
> it easy to add this counter.  Unfortunately, there is no analogous
> instrumentation in cxgbe so I couldn't do likewise for that NIC.)

Is this due to the other thread Rick has about TSO interacting with NFS?
Do these go away if you disable TSO on the interface?

-- 
John Baldwin