RE: [PATCH v1 4/6] net: fec: Increase buffer descriptor entry number

On Fri, 2014-05-30 at 15:08 +0000, fugang.duan@freescale.com wrote:

If frag page data is not match the alignment for ethernet DMA controller, there need three descriptor for one MSS:
One descriptor for headers, one for the first non-align bytes copied from frag page, one for the rest of frag page.

You could avoid the 2nd descriptor, by copying the unaligned part of the
payload into first descriptor (containing headers : about 66 bytes or so
you have room, if not, increase the 128 bytes room to 192 bytes)

So one frame may cost descriptor number is: 3 x 45 

May... but in general it would be closer of 2 * 45

So the descriptors slots set to 512 is not big, just is reasonable. Do you think ?

I believe it is fine : that is about 5 64KB TSO packets.