On 7/24/18 3:40 PM, John Fastabend wrote:
On 07/24/2018 08:45 AM, Yonghong Song wrote:
In one of our production machines, tools/testing/selftests/bpf
test_sockmap failed randomly like below:
...
[TEST 78]: (512, 1, 1, sendmsg, pass,apply 1,): rx thread exited with
err 1. FAILED
...
...
[TEST 80]: (2, 1024, 256, sendmsg, pass,apply 1,): rx thread exited with
err 1. FAILED
...
...
[TEST 83]: (100, 1, 5, sendpage, pass,apply 1,): rx thread exited with
err 1. FAILED
...
...
[TEST 79]: (512, 1, 1, sendpage, pass,apply 1,): rx thread exited with
err 1. FAILED
...
The command line is just `test_sockmap`. The machine has 80 cpus, 256G
memory. The kernel is based on 4.16 but backported with latest bpf-next
bpf changes.
The failed test number (78, 79, 80, or 83) is random. But they all share
similar characteristics:
. the option rate is greater than one, i.e., more than one
sendmsg/sendpage in the sender forked process.
. The txmsg_apply is not 0
I debugged a little bit. It happens in msg_loop() function below
"unexpected timeout" path.
...
slct = select(max_fd + 1, &w, NULL, NULL,
&timeout);
if (slct == -1) {
perror("select()");
clock_gettime(CLOCK_MONOTONIC, &s->end);
goto out_errno;
} else if (!slct) {
if (opt->verbose)
fprintf(stderr, "unexpected
timeout\n");
errno = -EIO;
clock_gettime(CLOCK_MONOTONIC, &s->end);
goto out_errno;
}
...
It appears that when the error happens, the receive process does not
receive all bytes sent from the send process and eventually times out.
Has anybody seen this issue as well?
John, any comments on this failure?
Can you run the test with verbose enabled so we can determine if the tx
side is even sending the message? Sample patch below. This will allow
us to see the tx bytes and rx bytes, although it will be a bit noisy.
I notice that the test program is not smart enough to (re)send bytes if
the sendmsg call doesn't consume all bytes. This is a valid error if
we get a enomem or other normal error on the tx side. With apply this
is more likely because every byte (in apply = 1 case) is being sent
through BPF prog.
The following are some of logs for the failed tests:
...
[TEST 78]: (512, 1, 1, sendmsg, pass,apply 1,): connected sockets: c1
<-> p1, c2 <-> p2
cgroups binding: c1(24) <-> s1(22) - - - c2(25) <-> s2(23)
tx_sendmsg: TX: 512B 0.000000B/s 0.000000 GB/s RX: 0B 0.000000B/s
0.000000GB/s
unexpected timeout
msg_loop_rx: iov_count 1 iov_buf 1 cnt 512 err -5
rx_sendmsg: TX: 0B 0.000000B/s 0.000000GB/s RX: 147B 147.000000B/s
0.000000GB/s
rx thread exited with err 1. FAILED
...
[TEST 82]: (100, 1, 5, sendmsg, pass,apply 1,): connected sockets: c1
<-> p1, c2 <-> p2
cgroups binding: c1(24) <-> s1(22) - - - c2(25) <-> s2(23)
tx_sendmsg: TX: 500B 0.000000B/s 0.000000 GB/s RX: 0B 0.000000B/s
0.000000GB/s
unexpected timeout
msg_loop_rx: iov_count 1 iov_buf 5 cnt 100 err -5
rx_sendmsg: TX: 0B 0.000000B/s 0.000000GB/s RX: 366B 366.000000B/s
0.000000GB/s
rx thread exited with err 1. FAILED
[TEST 402]: (512, 1, 1, sendmsg, pass,apply 1,): connected sockets: c1
<-> p1, c2 <-> p2
cgroups binding: c1(42) <-> s1(40) - - - c2(43) <-> s2(41)
tx_sendmsg: TX: 512B 0.000000B/s 0.000000 GB/s RX: 0B 0.000000B/s
0.000000GB/s
unexpected timeout
msg_loop_rx: iov_count 1 iov_buf 1 cnt 512 err -5
rx_sendmsg: TX: 0B 0.000000B/s 0.000000GB/s RX: 147B 147.000000B/s
0.000000GB/s
rx thread exited with err 1. FAILED
[TEST 80]: (2, 1024, 256, sendmsg, pass,apply 1,): connected sockets: c1
<-> p1, c2 <-> p2
cgroups binding: c1(24) <-> s1(22) - - - c2(25) <-> s2(23)
tx_sendmsg: TX: 524288B 0.000000B/s 0.000000 GB/s RX: 0B 0.000000B/s
0.000000GB/s
unexpected timeout
msg_loop_rx: iov_count 1024 iov_buf 256 cnt 2 err -5
rx_sendmsg: TX: 0B 0.000000B/s 0.000000GB/s RX: 458805B 458805.000000B/s
0.000459GB/s
rx thread exited with err 1. FAILED
If this is not the case I can do some more digging but I've not seen
this before.
I cannot reproduce it in my FC27 VM (with latest bpf-next) either.
The bug only shows up on our production service which is a lot busier
and has more cpus/memorys and some sysctl configurations are different
from my VM setup.
Thanks!
John
--- a/tools/testing/selftests/bpf/test_sockmap.c
+++ b/tools/testing/selftests/bpf/test_sockmap.c
@@ -1031,6 +1031,7 @@ static int test_exec(int cgrp, struct
sockmap_options *opt)
if (err)
goto out;
+ opt->verbose = true;
err = __test_exec(cgrp, SENDPAGE, opt);
out:
return err;
Thanks,
Yonghong
