> -----Original Message----- > From: Olivier MATZ [mailto:olivier.matz at 6wind.com] > Sent: Wednesday, February 11, 2015 1:07 AM > To: Zhang, Helin; dev at dpdk.org > Cc: Ananyev, Konstantin; Liu, Jijiang > Subject: Re: [PATCH v2 03/20] i40e: call i40e_txd_enable_checksum only for > offloaded packets > > Hi Helin, > > On 02/10/2015 07:03 AM, Zhang, Helin wrote: > >> /* Enable checksum offloading */ > >> cd_tunneling_params = 0; > >> - i40e_txd_enable_checksum(ol_flags, &td_cmd, &td_offset, > >> - l2_len, l3_len, outer_l2_len, > >> - outer_l3_len, > >> - &cd_tunneling_params); > >> + if (ol_flags & I40E_TX_CKSUM_OFFLOAD_MASK) { > > likely should be added. > > I would say unlikely() instead. I think the non-offload case should be the > default > one. What do you think? > > >> + i40e_txd_enable_checksum(ol_flags, &td_cmd, &td_offset, > >> + l2_len, l3_len, outer_l2_len, > >> + outer_l3_len, > >> + &cd_tunneling_params); > >> + } > > As this code changes are in fast path, performance regression test is > > needed. I would like to see the performance difference with or without > > this patch set. Hopefully nothing different. If you need any helps, just > > let me > know. > > I'm sorry, I won't have the needed resources to bench this as I would have to > setup a performance platform with i40e devices. > > But I'm pretty sure that the code in non-offload case would be faster with > this > patch as it will avoid many operations in i40e_txd_enable_checksum(). > > For the offload case, as we also removed the if (l2_len == 0) and if (l3_len > == 0), > I think there are also less tests than before my patch series. > > So in my opinion, adding this test does not really justify to check the > performance. As 40G is quite sensitive on cpu cycles, we'd better to avoid any performance drop during our modifying the code for fast path. Performance is what we care about too much. Based on my experiences, even minor code changes may result in big performance impact. It seems that we may need to help you on performance measurement.
Regards, Helin > > Regards, > Olivier
