[dpdk-dev] [PATCH v2 03/20] i40e: call i40e_txd_enable_checksum only for offloaded packets

[Olivier MATZ]

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.

Regards,
Olivier