Messages in this thread | | | Date | Wed, 5 Dec 2012 16:08:22 +0100 | From | Nicolas Ferre <> | Subject | Re: [PATCH] net/macb: increase RX buffer size for GEM |
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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
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