From: Eric Dumazet <eric.dumazet@xxxxxxxxx> Data: Friday, May 30, 2014 11:41 PM >To: Duan Fugang-B38611 >Cc: ezequiel.garcia@xxxxxxxxxxxxxxxxxx; David Laight; Li Frank-B20596; >davem@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; shawn.guo@xxxxxxxxxx; >bhutchings@xxxxxxxxxxxxxx; stephen@xxxxxxxxxxxxxxxxxx >Subject: RE: [PATCH v1 4/6] net: fec: Increase buffer descriptor entry >number > >On Fri, 2014-05-30 at 15:08 +0000, fugang.duan@xxxxxxxxxxxxx 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 > Good idea! > >> >> 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. > Thanks, Andy ��.n��������+%������w��{.n����z����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f