netdev - Re: random crashes, kdump and so on

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Message-ID: <CAM_iQpX=S9JEQzySy9nH5Ffp=pyeLFo4r9C9i=hb0UyAKot57g@mail.gmail.com>
Date:   Mon, 25 Mar 2019 12:07:12 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Reindl Harald <h.reindl@...lounge.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: random crashes, kdump and so on

On Mon, Mar 25, 2019 at 5:08 AM Reindl Harald <h.reindl@...lounge.net> wrote:
>
> besides that i get tired about random crashes over the last months (yeah
> the connlimit crashes are fixed in the meantime but there is still
> something broken) which are pretty sure in the netedev/netfilter area
> and "kernel.panic = 1" is not a persistent solution
>
> what in the world makes kdump on a VM with 2.5 GB RAM dump out 5.4GB and
> why do you need a handful reboots to get rid of "Can't find kernel text
> map area from kcore" when try to start the kdump service?

Possibly because of KASLR, please report this to kexec-tools mailing
list. This looks more like a kexec-tools bug than a kernel bug.


>
> why can't the kernel just write out what it normally prints on the
> screen to a fixed device like /dev/sdc without that whole dance, no
> filesystem needed, just write it out like d and reboot

It can, but many times stack traces are not sufficient for debugging
a kernel crash. This is why kdump saves the whole memory.


>
> sdc is stable on a VM and the terminal output has cutted every relevant
> information when you wait for HA of the hypervisor make a screenshot
> before hard reset instead the automatic reboot from the guest
>
> can we please get Linux as stable as it was or better to debug in
> production so that one can submit useful infos in bugreports?


Switch to a stable distro, like CentOS or Debian stable. If you use
Fedora 28, it is expected to be not that stable (relatively).

Thanks.