netdev - Re: [PATCH net-next] selftests/net: force synchronized GC for a test.

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Message-ID: <d0719417-e67f-48a9-ac1a-970d0c405270@kernel.org>
Date: Mon, 4 Mar 2024 19:41:07 -0700
From: David Ahern <dsahern@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>, Kui-Feng Lee <sinquersw@...il.com>
Cc: Kui-Feng Lee <thinker.li@...il.com>, netdev@...r.kernel.org,
 ast@...nel.org, martin.lau@...ux.dev, kernel-team@...a.com,
 davem@...emloft.net, kuifeng@...a.com
Subject: Re: [PATCH net-next] selftests/net: force synchronized GC for a test.

On 3/4/24 8:44 AM, Jakub Kicinski wrote:
> On Fri, 1 Mar 2024 16:45:58 -0800 Kui-Feng Lee wrote:
>> However, some extra waiting may be added to it.
>> There are two possible extra waiting. The first one is calling
>> round_jiffies() in fib6_run_gc(), that may add 750ms at most. The second
>> one is the granularity of waiting for 5 seconds (in our case) is 512ms
>> for HZ 1000 according to the comment at the very begin of timer.c.
>> In fact, it can add 392ms for 5750ms (5000ms + 750ms). Overall, they may
>> contribute up to 1144ms.
>>
>> Does that make sense?
>>
>> Debug build is slower. So, the test scripts will be slower than normal
>> build. That means the script is actually waiting longer with a debug build.
> 
> Meaning bumping the wait to $((($EXPIRE + 1) * 2))
> should be enough for the non-debug runner?

I have not had time to do a deep a dive on the timing, but it seems odd
to me that a 1 second timer can turn into 11 sec. That means for 10
seconds (10x the time the user requested) the route survived.