NIC - Receive Buffer Size - MTU

[tsdnz]

Hi all, In the Intel "pcie-gbe-controllers-open-source-manual.pdf" manual there is a field BSIZE (Receive Buffer Size).

Receive Buffer Size
Controls the size of the receive buffers, allowing the software to
trade off between system performance and storage space. Small
buffers maximize memory efficiency at the cost of multiple
descriptors for bigger packets.
RCTL.BSEX = 0b:
00b = 2048 Bytes.
01b = 1024 Bytes.
10b = 512 Bytes.
11b = 256 Bytes.
RCTL.BSEX = 1b:
00b = Reserved; software should not program this value.
01b = 16384 Bytes.
10b = 8192 Bytes.
11b = 4096 Bytes.
Note: BSIZE is only used when DTYP = 00b. When DTYP = 01b,
the buffer sizes for the descriptor are controlled by fields in the
Packet Split Receive Control (PSRCTL) register.
BSIZE is not relevant when FLXBUF is something other than 0b. in
that case, FLXBUF determines the buffer size.

How is this field used?
If I set it to 16384B does it automatically concatenate the packets or the data, or something else?

Alistair.

[alexfru]

Have you tried searching for this register name in the document? Have you tried looking at the DPDK or Linux/BSD driver code?
If not, why not? You should be able to find this info in there.

[tsdnz]

It must be to just split large packets