Re: [PATCH bpf-next 10/14] mlx5, xsk: migrate to new MEM_TYPE_XSK_BUFF_POOL

On 2020-05-08 13:55, Maxim Mikityanskiy wrote:

On 2020-05-07 13:42, Björn Töpel wrote:

quoted

From: Björn Töpel <redacted>

Use the new MEM_TYPE_XSK_BUFF_POOL API in lieu of MEM_TYPE_ZERO_COPY in
mlx5e. It allows to drop a lot of code from the driver (which is now
common in AF_XDP core and was related to XSK RX frame allocation, DMA
mapping, etc.) and slightly improve performance.

rfc->v1: Put back the sanity check for XSK params, use XSK API to get
          the total headroom size. (Maxim)

Signed-off-by: Björn Töpel <redacted>
Signed-off-by: Maxim Mikityanskiy <redacted>

I did some functional and performance tests.

Unfortunately, something is wrong with the traffic: I get zeros in 
XDP_TX, XDP_PASS and XSK instead of packet data. I set DEBUG_HEXDUMP in 
xdpsock, and it shows the packets of the correct length, but all bytes 
are 0 after these patches. It might be wrong xdp_buff pointers, however, 
I still have to investigate it. Björn, does it also affect Intel 
drivers, or is it Mellanox-specific?

Are you getting zeros for TX, PASS *and* in xdpsock (REDIRECT:ed 
packets), or just TX and PASS?

No, I get correct packet data for AF_XDP zero-copy XDP_REDIRECT,
XDP_PASS, and XDP_TX for Intel.

For performance, I got +1.0..+1.2 Mpps on RX. TX performance got better 
after Björn inlined the relevant UMEM functions, however, there is still 
a slight decrease compared to the old code. I'll try to find the 
possible reason, but the good thing is that it's not significant anymore.

Ok, so for Rx mlx5 it's the same as for i40e. Good! :-)

How much decrease on Tx?


Björn