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From: "David Christensen" <davidch@broadcom.com>
To: "pyunyh@gmail.com" <pyunyh@gmail.com>,
	"Andre Oppermann" <andre@freebsd.org>
Date: Mon, 13 Sep 2010 15:21:13 -0700
Thread-Topic: bce(4) - com_no_buffers (Again)
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Cc: Tom Judge <tom@tomjudge.com>,
	"freebsd-net@freebsd.org" <freebsd-net@freebsd.org>,
	"yongari@freebsd.org" <yongari@freebsd.org>
Subject: RE: bce(4) - com_no_buffers (Again)
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> I'm under the impression the header splitting in bce(4) is for
> LRO(opposite of TSO), not for VM magic to enable page flipping
> tricks.

Header splitting was implemented in the Linux version of bce(4)
to prevent jumbo memory allocations.  Allocating 9KB frames was
causing problems on systems used for virtualization.  (Harder to
find a contiguous 9KB frame when a hypervisor is in use.)  Using=20
4KB or smaller buffer sizes was considered more compatible with
virtualization. =20

LRO (Large Receive Offload, aka Transparent Packet Aggregation
or TPA on the 10Gb controllers) is not supported on the 1Gb=20
bce(4) devices.

Dave