CentOS - Jun 2020 - CentOS 7 system running out of available memory, then unusable, network interfaces probably involved

Hello,

my CentOS 7 system goes unstable after few days of use, memory
consumption growing and never getting freed, until the system slows
down to hell (swapping), kills apps, and eventually freezes or reboots
itself.

This only happens when I have two network interfaces turned on, one
wired and one wireless, each to different routers.

The hardware: a Dell Precision 7530, SSD, 16GB RAM. HW memory and disk
both tested OK by software.
According to lspci:
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (7) I219-LM
(rev 10)
6e:00.0 Network controller: Intel Corporation Wireless-AC 9260 (rev 29)

The software: I keep this CentOS 7 system up-to-date with the CR repo,
excepted the microcode_ctl package, stuck to few versions back
(updating it kills the system and potentially causes fs damages).
Kernels reproducing the issue (IOW, all):
  kernel-3.10.0-1062.18.1.el7.x86_64
  kernel-3.10.0-1127.el7.x86_64
  kernel-3.10.0-1127.8.2.el7.x86_64
  kernel-3.10.0-1127.13.1.el7.x86_64

Nothing jumps to my eyes looking at /var/log/messages but this, many
occurrences:
  kernel: nf_conntrack: falling back to vmalloc.
I searched the Internet for it, and the few results I found were
not bringing any solution and were quite pessimistic WRT to memory
freeing, am I wrong?

Regards,

-- 
wwp
https://useplaintext.email/
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On Mon, Jun 29, 2020 at 12:47 PM wwp <subscript at free.fr> wrote:
>
> Nothing jumps to my eyes looking at /var/log/messages but this, many
> occurrences:
>   kernel: nf_conntrack: falling back to vmalloc.
>
nf_conntrack is only involved if you are doing some form of NAT routing on
this system and/or fairly complex iptables kind of rules....  you mentioned
two different network interfaces, one wired, one wireless, how are you
using these, what sort of routing between the two networks ?



-- 
-john r pierce
  recycling used bits in santa cruz

Hello John,


On Mon, 29 Jun 2020 12:54:58 -0700 John Pierce <jhn.pierce at gmail.com>
wrote:
> On Mon, Jun 29, 2020 at 12:47 PM wwp <subscript at free.fr> wrote:
> 
> >
> > Nothing jumps to my eyes looking at /var/log/messages but this, many
> > occurrences:
> >   kernel: nf_conntrack: falling back to vmalloc.
> >  
> 
> nf_conntrack is only involved if you are doing some form of NAT routing on
> this system and/or fairly complex iptables kind of rules....
On this machine I do not do anything at iptables or firewall level but
opening ports for SSHD.

> you mentioned two different network interfaces, one wired, one
> wireless, how are you using these, what sort of routing between the
> two networks ?
The wired interface is directly bound to a 4G router (dhcp).
The wireless one is connected to a LAN (wifi -> wifi AP -> wire ->
switch ->
wire -> router with iptables+dhcp -> wire -> xDSL box).


Regards,

-- 
wwp
https://useplaintext.email/
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