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@xxxxxxxxxxxxx
authenticity, honesty, community
http://dancingtreefrog.com
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