On Sat, Dec 5, 2020 at 1:03 PM Mohamed Abuelfotoh, Hazem
<abuehaze(a)amazon.com> wrote:
>
> Unfortunately few things are missing in this report.
>
> What is the RTT between hosts in your test ?
> >>>>>RTT in my test is 162 msec, but I am able to reproduce it with lower RTTs for example I could see the issue downloading from google endpoint with RTT of 16.7 msec, as mentioned in my previous e-mail the issue is reproducible whenever RTT exceeded 12msec given that the sender is using bbr.
>
> RTT between hosts where I run the iperf test.
> # ping 54.199.163.187
> PING 54.199.163.187 (54.199.163.187) 56(84) bytes of data.
> 64 bytes from 54.199.163.187: icmp_seq=1 ttl=33 time=162 ms
> 64 bytes from 54.199.163.187: icmp_seq=2 ttl=33 time=162 ms
> 64 bytes from 54.199.163.187: icmp_seq=3 ttl=33 time=162 ms
> 64 bytes from 54.199.163.187: icmp_seq=4 ttl=33 time=162 ms
>
> RTT between my EC2 instances and google endpoint.
> # ping 172.217.4.240
> PING 172.217.4.240 (172.217.4.240) 56(84) bytes of data.
> 64 bytes from 172.217.4.240: icmp_seq=1 ttl=101 time=16.7 ms
> 64 bytes from 172.217.4.240: icmp_seq=2 ttl=101 time=16.7 ms
> 64 bytes from 172.217.4.240: icmp_seq=3 ttl=101 time=16.7 ms
> 64 bytes from 172.217.4.240: icmp_seq=4 ttl=101 time=16.7 ms
>
> What driver is used at the receiving side ?
> >>>>>>I am using ENA driver version version: 2.2.10g on the receiver with scatter gathering enabled.
>
> # ethtool -k eth0 | grep scatter-gather
> scatter-gather: on
> tx-scatter-gather: on
> tx-scatter-gather-fraglist: off [fixed]
This ethtool output refers to TX scatter gather, which is not relevant
for this bug.
I see ENA driver might use 16 KB per incoming packet (if ENA_PAGE_SIZE is 16 KB)
Since I can not reproduce this problem with another NIC on x86, I
really wonder if this is not an issue with ENA driver on PowerPC
perhaps ?
Hi Sasha-
This v5.4.78 commit breaks the tools/testing/selftests/bpf build:
[linux-5.4.y] c602ad2b52dc bpf: Zero-fill re-used per-cpu map element
Like this:
prog_tests/map_init.c:5:10: fatal error: test_map_init.skel.h: No such file or directory
5 | #include "test_map_init.skel.h"
Because tools/testing/selftests/bpf/Makefile in v5.4 does not have the
"skeleton header generation" stuff (circa v5.6).
Reverting c602ad2b52dc from linux-5.4.y fixes it.
-Kamal