[LAU] reducing xruns (System configuration)

[david]

On 07/19/2018 10:17 PM, Ralf Mardorf wrote:
> On Thu, 19 Jul 2018 20:25:42 -1000, david wrote:
>> 4.8 doesn't have the Spectre/Meltdown patches. 4.16 does. So I blame
>> the Spectre/Meltdown patches.
> 
> I already pointed tis out by an earlier mail:
> 
> "I didn't test, if the page table isolation stuff has got impact on
> real-time performance, maybe you want to disable it, if so add 'nopti':
> 
> [rocketmouse at archlinux ~]$ grep -A3
> '\^nopti' /boot/syslinux/syslinux.cfg MENU LABEL Arch Linux threadirqs
> ^nopti LINUX ../vmlinuz-linux
>      APPEND root=LABEL=archlinux ro threadirqs nopti
>      INITRD ../intel-ucode.img,../initramfs-linux.img" -
> 
> https://lists.linuxaudio.org/archives/linux-audio-user/2018-July/110576.html
> 
> By the kernel package's changelog you could see if 'nopti' is
> available. For older official Ubuntu kernels is was 'nokaiser', but for
> all current official Ubuntu kernels it is 'nopti'.
> 
> The output of
> 
> ls -hAl /sys/devices/system/cpu/vulnerabilities/; cat /sys/devices/system/cpu/vulnerabilities/*
> 
> shows if PTI mitigation is enabled at all.

And I figured out where to put pti=off on my various GRUB lines, so now 
it boots with it off. And my desktop latency is back to 10msecs. :)

My understanding is that any post-4.13.x kernel has the Spectre/Meltdown 
patches. I first tried it with 4.13.x and decided that items like random 
kernel panios, system freezes and crashes weren't very good ways to 
defend against Spectre/Meltdown/DOS. ;)

-- 
David W. Jones
gnome at hawaii.rr.com
authenticity, honesty, community
http://dancingtreefrog.com