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From: Andrew Gallatin <gallatin@cs.duke.edu>
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Date: Tue, 20 Aug 2002 16:07:14 -0400 (EDT)
To: Julian Elischer <julian@elischer.org>
Cc: freebsd-net@FreeBSD.ORG
Subject: Re: m_getcl and end-to-end performance
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Julian Elischer writes:
 > > Yes, it checks that M_EXT_WRITABLE(m) is true before adding it to the pool.
 > 
 > Are only Cluster mbufs writable?

Yes.  At least in -stable:

#define M_EXT_WRITABLE(m)       \
    ((m)->m_ext.ext_free == NULL && mclrefcnt[mtocl((m)->m_ext.ext_buf)] == 1)


Drew

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