netdev - Re: IPv6 regression introduced by commit 3b6761d18bc11f2af2a6fc494e9026d39593f22c

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Date:   Tue, 10 Mar 2020 11:35:41 +0100
From:   Alarig Le Lay <alarig@...rdarmor.fr>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org, jack@...ilfillan.uk,
        Vincent Bernat <bernat@...ian.org>
Subject: Re: IPv6 regression introduced by commit
 3b6761d18bc11f2af2a6fc494e9026d39593f22c

On dim.  8 mars 20:15:14 2020, David Ahern wrote:
> If you are using x86 based CPU you can do this:
>     perf probe ip6_dst_alloc%return ret=%ax
> 
>     perf record -e probe:* -a -g -- sleep 10
>     --> run this during the flapping
> 
>     perf script

For this probe I see that: https://paste.swordarmor.fr/raw/pt9b

> this will show if the flapping is due to dst alloc failures.
> 
> Other things to try:
>     perf probe ip6_dst_gc
>     perf stat -e probe:* -a -I 1000
>     --> will show calls/sec to running dst gc

https://paste.swordarmor.fr/raw/uBnm

>     perf probe __ip6_rt_update_pmtu
>     perf stat -e probe:* -a -I 1000
>     --> will show calls/sec to mtu updating

This probe always stays at 0 even when the NDP is failing.
 
>     perf probe rt6_insert_exception
>     perf state -e probe:* -a -I 1000
>     --> shows calls/sec to inserting exceptions

Same as the last one.

> (in each you can remove the previous probe using 'perf probe -d <name>'
> or use -e <exact name> to only see data for the one event).
> 
> > I have the problem with 5.3 (proxmox 6), so unless FIB handling has been
> > changed since then, I doubt that it will works, but I will try on
> > Monday.
> > 
> 
> a fair amount of changes went in through 5.4 including improvements to
> neighbor handling. 5.4 (I think) also had changes around dumping the
> route cache.

Regards,
-- 
Alarig