On 11/26/2017 10:41 AM, Shahaf Shuler wrote:
>>+ .ignore_offload_bitfield = 1,
>>+ .offloads = DEV_RX_OFFLOAD_CRC_STRIP,
>
>It is not directly related to the patch.
>May be I miss something, but it looks like there is no way to say that
>"I always strip CRC and cannot preserve it".
Yes this is right. Not exposing the CRC offload flag means the device
don’t support CRC strip toggling, however it does not explicitly say
if device always strip/not.
I guess device that has such limitation should specify it on the
“Limitation” section of the PMD guide.
If it is interpreted in such way it sounds like loss of functionality.
Don't think it is a good way to rely on documentation here. It should
be more reliable way. PMD still can check if offload is not enabled and
complain, but there is no way to say that it is strictly required.
As I understand similar things are covered with so-called fixed offloads
in Linux.
>>+ txq_conf = dev_info.default_txconf;
>>+ txq_conf.txq_flags = ETH_TXQ_FLAGS_IGNORE;
>>+ txq_conf.offloads = port_conf.txmode.offloads;
>
>It looks like it is not 100% equivalent. As far as I can see dev_info
get does
>not convert txq_flags to offloads in default_txconf and in any case
txq_conf.offloads
>are overwritten here. So, if PMD provides default txq_flags, it is lost.
>If it is intentionally, it should be highlighted and explained.
Yes it is.
With the new Tx offloads API the application can choose the Tx
offloads it wants to use according to its needs.
For l2fwd case – it doesn’t use any of them. Any default txq flag the
PMD set there is irrelevant.
What I tried to do is not to preserve the entire old behavior rather
to evolve the examples/applications while keeping the same
functionality (i.e. the offloads which the application use are set,
the rest are not).
That's true for checksum and VLAN offloads, but false for fast-free.
As I understand l2fwd and many other examples meet fast-free
requirements and if PMD supports it, it should be used since it will
show better performance results.
Moreover – it is a wrong approach, IMO, that the PMD set default
offloads flags to the application. It has no knowledge to do so. I
think this mechanism was initially created since the Tx offloads were
all set by default, so it provided a mean to have good OOB
configuration. Now when all offloads are set, I am not sure such API
is needed anymore.
Will be happy to hear more opinion on that.
I agree that blindly using PMD default offloads is a wrong approach.
