netdev - Re: [PATCH net-next v4 11/11] bpf: add simple bpf tests in the tx path for so

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Message-ID: <14464b87-aaf4-4879-89ae-2006c1024fab@linux.dev>
Date: Fri, 13 Dec 2024 16:14:05 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com,
 willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, bpf@...r.kernel.org,
 netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v4 11/11] bpf: add simple bpf tests in the tx
 path for so_timstamping feature

On 12/13/24 8:02 AM, Jason Xing wrote:
>>> +static u64 delay_tolerance_nsec = 5000000;
>>
>> If I count right, 5ms may not a lot for the bpf CI and the test could become
>> flaky. Probably good enough to ensure the delay is larger than the previous one.
> 
> You're right, initially I set 2ms which make the test flaky. How about
> 20ms? We cannot ensure each delta (calculated between two tx points)
> is larger than the previous one.

or I was thinking the delay is always measured from sendmsg_ns.

Regardless, whatever way the delay of a tx point is measured from (always from 
sendmsg_ns or from the previous tx point), it can also just check the measured 
delay is +ve or something like that instead of having a hard coded maximum delay 
here.

The following "struct delay_info" may not be the best. Feel free to adjust.

>> struct delay_info {
>>          u64 sendmsg_ns;
>>          u32 sched_delay;  /* SCHED_OPT_CB - sendmsg_ns */
>>          u32 sw_snd_delay;
>>          u32 ack_delay;
>> };