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Date:      Sun, 24 Nov 2002 13:33:29 -0800 (PST)
From:      Julian Elischer <julian@elischer.org>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        Robert Watson <rwatson@freebsd.org>, Luigi Rizzo <rizzo@icir.org>, current@freebsd.org
Subject:   Re: mbuf header bloat ?
Message-ID:  <Pine.BSF.4.21.0211241332190.34466-100000@InterJet.elischer.org>
In-Reply-To: <15841.17237.826666.653505@grasshopper.cs.duke.edu>

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On Sun, 24 Nov 2002, Andrew Gallatin wrote:

> 
> If we're going to nitpick the mbuf system, a much, much worse problem
> is that you cannot allocate an mbuf chain w/o holding Giant, which
> stems from the mbuf system eventually calling kmem_malloc().  This
> effectively prevents any network driver from being giant-free.  When
> mbufs are low, mb_alloc() calls mb_pop_cont().  This, in turn, calls
> kmem_malloc() which requires Giant...
> 
> The mbuf system calls malloc in other ways too.  The first time you
> use a cluster, m_ext.ext_ref_cnt is malloc()'ed, and malloc is called
> when the mbuf map is expanded...   I assume malloc will eventually
> call kmem_malloc(), leading to the same locking problems.
> 
> I know that both tru64 and aix just malloc their mbufs.

I think we tied that and went back to a separate allocator, but I have
no idea why..  maybe someone else can enlighten me..


> 
> Drew
> 
> 
> 


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