From: nicolas.ferre@atmel•com (Nicolas Ferre)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] net/macb: increase RX buffer size for GEM
Date: Wed, 5 Dec 2012 16:08:22 +0100 [thread overview]
Message-ID: <50BF6366.8080600@atmel.com> (raw)
In-Reply-To: <20121204.132227.1430662061932892582.davem@davemloft.net>
On 12/04/2012 07:22 PM, David Miller :
> From: Nicolas Ferre <nicolas.ferre@atmel•com>
> Date: Mon, 3 Dec 2012 13:15:43 +0100
>
>> Macb Ethernet controller requires a RX buffer of 128 bytes. It is
>> highly sub-optimal for Gigabit-capable GEM that is able to use
>> a bigger DMA buffer. Change this constant and associated macros
>> with data stored in the private structure.
>> I also kept the result of buffers per page calculation to lower the
>> impact of this move to a variable rx buffer size on rx hot path.
>> RX DMA buffer size has to be multiple of 64 bytes as indicated in
>> DMA Configuration Register specification.
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel•com>
>
> This looks like it will waste a couple hundred bytes for 1500 MTU
> frames, am I right?
Yep! But buffers get recycled, and with the current memory management by
pages, it seems that I have to rework some part of it to optimize this
memory usage (8KB memory blocks split into 5 buffers each as David said...).
Do you think it is worth digging this way or may I rework the rx buffer
management in case of the GEM interface. If I implement a different path
for GEM interface, I will have the possibility to tailor rx DMA buffers
from 1500 Bytes up to 10KB jumbo frames...
Best regards,
--
Nicolas Ferre
next prev parent reply other threads:[~2012-12-05 15:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-03 12:15 [PATCH] net/macb: increase RX buffer size for GEM Nicolas Ferre
2012-12-04 18:22 ` David Miller
2012-12-05 15:08 ` Nicolas Ferre [this message]
2012-12-05 17:58 ` David Miller
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