netdev - Re: iproute2: tc deletion freezes whole server

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Date:   Mon, 4 May 2020 13:36:45 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Václav Zindulka <vaclav.zindulka@...pnet.cz>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: iproute2: tc deletion freezes whole server

On Mon, May 4, 2020 at 10:46 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> Regarding to your test result above, I think I saw some difference
> on my side, I have no idea why you didn't see any difference. Please
> let me collect the data once I setup the test environment shortly today.

I tried to emulate your test case in my VM, here is the script I use:

====
ip li set dev dummy0 up
tc qd add dev dummy0 root handle 1: htb default 1
for i in `seq 1 1000`
do
  tc class add dev dummy0 parent 1:0 classid 1:$i htb rate 1mbit ceil 1.5mbit
  tc qd add dev dummy0 parent 1:$i fq_codel
done

time tc qd del dev dummy0 root
====

And this is the result:

    Before my patch:
     real   0m0.488s
     user   0m0.000s
     sys    0m0.325s

    After my patch:
     real   0m0.180s
     user   0m0.000s
     sys    0m0.132s

This is an obvious improvement, so I have no idea why you didn't
catch any difference.

Thanks.