Date: Tue, 4 Feb 2014 23:08:21 -0700 From: Scott Long <scott4long@yahoo.com> To: Garrett Wollman <wollman@freebsd.org> Cc: FreeBSD Net <freebsd-net@freebsd.org>, rmacklem@freebsd.org Subject: Re: ixgbe/NFS m_defrag() instrumentation Message-ID: <E6B5E96C-A579-4187-B2FB-61B6B5E90D7F@yahoo.com> In-Reply-To: <21233.52147.912022.488615@hergotha.csail.mit.edu> References: <21233.52147.912022.488615@hergotha.csail.mit.edu>
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On Feb 4, 2014, at 10:27 PM, Garrett Wollman <wollman@freebsd.org> 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.)
dtrace to the rescue?
#!/usr/sbin/dtrace -s
fbt::m_defrag:entry
{
@ = count();
}
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