[dpdk-dev] ixgbe_recv_scattered_pkts_vec split_flags question

[dpdk-dev] ixgbe_recv_scattered_pkts_vec split_flags question

[Zoltan Kiss]

Hi,

I have a question regarding split_flags in this question. It's defined 
as an array of 1 byte unsigned ints:

uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0};

RTE_IXGBE_VPMD_RX_BURST is 32, so it will be 32 bytes. Then we cast it 
into a pointer for 4 byte values, and check the first 4 elements of that 
array

const uint32_t *split_fl32 = (uint32_t *)split_flags;
if (rxq->pkt_first_seg == NULL &&
		split_fl32[0] == 0 && split_fl32[1] == 0 &&
		split_fl32[2] == 0 && split_fl32[3] == 0)

So we only check the first half of this 32 byte array. But 
_recv_raw_pkts_vec() seems to use the whole array. Is this a bug or a 
feature? Or am I mistaken in the math somewhere?

Regards,

Zoltan Kiss

Re: [dpdk-dev] ixgbe_recv_scattered_pkts_vec split_flags question

[Bruce Richardson]

On Tue, Jul 21, 2015 at 04:09:59PM +0100, Zoltan Kiss wrote:
> Hi,
> 
> I have a question regarding split_flags in this question. It's defined as an
> array of 1 byte unsigned ints:
> 
> uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0};
> 
> RTE_IXGBE_VPMD_RX_BURST is 32, so it will be 32 bytes. Then we cast it into
> a pointer for 4 byte values, and check the first 4 elements of that array
> 
> const uint32_t *split_fl32 = (uint32_t *)split_flags;
> if (rxq->pkt_first_seg == NULL &&
> 		split_fl32[0] == 0 && split_fl32[1] == 0 &&
> 		split_fl32[2] == 0 && split_fl32[3] == 0)
> 
> So we only check the first half of this 32 byte array. But
> _recv_raw_pkts_vec() seems to use the whole array. Is this a bug or a
> feature? Or am I mistaken in the math somewhere?
> 
> Regards,
> 
> Zoltan Kiss

Yes, you are right, this does look like a bug. The uint32_t's should probably be
uint64_t's. :-(

/Bruce