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Date:      Tue, 07 Nov 2006 11:59:11 -0500
From:      Randall Stewart <rrs@cisco.com>
To:        sivakumar.subramani@wipro.com
Cc:        freebsd-net@freebsd.org, freebsd-stable@freebsd.org
Subject:   Re: Regarding Jumbo frame implementation in bge
Message-ID:  <4550BB5F.3040101@cisco.com>
In-Reply-To: <821C7AD2A9F78942B86059792262577315B072@blr-m3-msg.wipro.com>
References:  <821C7AD2A9F78942B86059792262577315B072@blr-m3-msg.wipro.com>

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sivakumar.subramani@wipro.com wrote:
> Hi,
> 
> In bge driver, we have BGE_JUMBO_FRAMELEN defined to 9018. 
> if_bgereg.h:#define BGE_JUMBO_FRAMELEN  9018
> 
> This macro is used to allocate the memory for jumbo buffer. If I have
> a MTU size of 2000, still bge will allocate the jumbo buffer of size 
> BGE_JUMBO_FRAMELEN. Instead can we make the size to be depend on the 
> MTU. I mean instead of using BGE_JUMBO_FRAMELEN macro we can use MTU
> + IP header + CRC for Jumbo buffer size.
> 
> Any reason for allocating a hard coded 9018 size all Jumbo MTU frame 
> (whether it is 9000 / 2000)?
> 
> Thanks, ~Siva
>
Sivakumar:

Allocations are done via the zone managers.. and thus setup
at kernel boot. A value like the MTU is set dynamically...

So doing something like this would be questionable IMO.. I
am sure it could be done.. but I don't see the value.
In theory you have a waste for just a short time.. before
its m_free'd


R

-- 
Randall Stewart
NSSTG - Cisco Systems Inc.
803-345-0369 <or> 803-317-4952 (cell)



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