pfactum

1. 100% on laptop and *almost* always on QEMU.

For QEMU I use the following command with a minimal kernel:

$ qemu-system-x86_64 -machine q35,accel=kvm -cpu core2duo -smp cores=8,threads=2 -kernel arch/x86/boot/bzImage -append "ignore_loglevel threadirqs nokaslr"

I've added "threadirqs", because it triggers the issue in the VM more reliably (lots of threads to schedule at early stages). On a real machine the issue is reproducible without this option too.

Minimal kernel config: [1]

pfactum

[    0.000000] Linux version 4.19.0-pf7+ (pf@spock) (gcc version 8.2.1 20181127 (GCC)) #1 SMP PREEMPT Fri Dec 7 10:24:43 CET 2018
[    0.000000] Command line: ignore_loglevel threadirqs nokaslr
[    0.000000] x86/fpu: x87 FPU will use FXSAVE
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000007fdefff] usable
[    0.000000] BIOS-e820: [mem 0x0000000007fdf000-0x0000000007ffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved

pfactum

#
# Automatically generated file; DO NOT EDIT.
# Linux/x86 4.19.0-pf7 Kernel Configuration
#

#
# Compiler: gcc (GCC) 8.2.1 20181127
#
CONFIG_CC_IS_GCC=y
CONFIG_GCC_VERSION=80201

pfactum

[    2.504941] smp: Brought up 1 node, 4 CPUs                                                                                         
[    2.510787] smpboot: Max logical packages: 1                                                                                       
[    2.514909] smpboot: Total of 4 processors activated (12800.00 BogoMIPS)                                                           
[    2.528811] pds: cpu #0 affinity check mask - smt 0x00000002                                                                       
[    2.528816] pds: cpu #0 affinity check mask - coregroup 0x0000000e                                                                 
[    2.534857] pds: cpu #1 affinity check mask - smt 0x00000001                                                                       
[    2.544831] pds: cpu #1 affinity check mask - coregroup 0x0000000d                                                                 
[    2.554853] pds: cpu #2 affinity check mask - smt 0x00000008                

pfactum

» sudo ethtool -k enp3s0 | grep -v fixed
Features for enp3s0:
rx-checksumming: on
tx-checksumming: off
        tx-checksum-ipv4: off
        tx-checksum-ipv6: off
scatter-gather: on
        tx-scatter-gather: on
tcp-segmentation-offload: off
        tx-tcp-segmentation: off

pfactum

/etc/sysctl.d » cat *
net.ipv4.ip_nonlocal_bind = 1
net.ipv6.ip_nonlocal_bind = 1
net.ipv4.ip_local_port_range = 1026 59999
net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1
net.ipv6.route.max_size = 16384
net.ipv4.ip_dynaddr = 1
net.ipv4.tcp_mtu_probing = 1
net.ipv4.tcp_congestion_control = bbr

pfactum

#!/usr/bin/env bash

# Examples:
#	bufferbloat start eth0 20 20
#	bufferbloat stop eth0

self="$(basename $(/usr/bin/realpath ${0}))"
isp_uplink="${2}"
isp_downlink="ifb0"
max_download="${3}"

pfactum

#!/usr/bin/env bash

delay="1000"
pid1=`pidof hostapd`

if [[ $pid1 != "" ]]
then
	notify-send -t $delay "Зупиняю точку доступу Wi-Fi…"
	sudo iptables -t nat -F
	sudo iptables -t mangle -F

pfactum

# Maintainer: Oleksandr Natalenko <oleksandr@natalenko.name>

pkgname=("intel-c-compiler")
__year=2018
__update=3
__build=222
__id=13002
pkgver=${__year}.${__update}
pkgrel=1

pfactum

Core was generated by `/usr/bin/nft flush ruleset ; include "/etc/nftables.conf"'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f6b151d33a4 in input_descriptor_dup (indesc=0x0) at erec.c:52
52      erec.c: No such file or directory.
(gdb) bt
#0  0x00007f6b151d33a4 in input_descriptor_dup (indesc=0x0) at erec.c:52
#1  0x00007f6b151d349a in erec_add_location (erec=0x55a2617c8720, loc=<optimized out>) at erec.c:69
#2  0x00007f6b151d3559 in erec_vcreate (type=type@entry=EREC_ERROR, loc=0x55a2722c24b0, 
    fmt=0x7f6b151eb77c "Could not process rule: %s", ap=ap@entry=0x7ffd9d79b540) at erec.c:94
#3  0x00007f6b151c53fe in netlink_io_error (ctx=ctx@entry=0x7ffd9d79b680, loc=<optimized out>, loc@entry=0x55a2722c24b0,