28 May 2021, 20:59

Make Linux Fast Again

https://make-linux-fast-again.com/ has big promises, boy oh boy. I was wondering how much I should blame the recent spate of hardware vulnerability mitigations for my laptop being pokey, so I decided to turn it off. Slamming all of those options blindly into my kernel command line worked OK- but nothing perceptible happened.

/proc/cmdline is the place to go to check your changes worked end-to-end, by the way.

I was, however, oddly locked out of Flatpak- but was seeing this in the kernel logs-

flatpak-portal[1967]: segfault at c ip 000055665f85f8d0 sp 00007ffce0ffa800 error 4 in flatpak-portal[55665f83f000+d4000]

seems bad, right? Cutting back the kernel flags to just mitigations=off fixed Flatpak, and I’m still Living Dangerously-

$ grep . /sys/devices/system/cpu/vulnerabilities/*
/sys/devices/system/cpu/vulnerabilities/itlb_multihit:KVM: Vulnerable
/sys/devices/system/cpu/vulnerabilities/l1tf:Mitigation: PTE Inversion; VMX: vulnerable
/sys/devices/system/cpu/vulnerabilities/mds:Vulnerable; SMT vulnerable
/sys/devices/system/cpu/vulnerabilities/meltdown:Vulnerable
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass:Vulnerable
/sys/devices/system/cpu/vulnerabilities/spectre_v1:Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers
/sys/devices/system/cpu/vulnerabilities/spectre_v2:Vulnerable, IBPB: disabled, STIBP: disabled
/sys/devices/system/cpu/vulnerabilities/srbds:Vulnerable
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort:Not affected

So, I’m an old web dork, and I don’t have any go-to benchmarks to go by, but I vaguely remember Octane being important like ten years ago, and I don’t have to install anything- and they’re CPU benchmarks, which is sort of relevant. So here’s a baseline, with mitigations on-

Octane Score: 10622 (mitigations=on, firefox)
Octane Score: 10814 (mitigations=on, firefox)
Octane Score: 24399 (mitigations=on, chrome)
Octane Score: 24858 (mitigations=on, chrome)

Wow! Chrome is a lot better at this than Firefox. I mean, it’s their benchmark, but wow!

With all of the Spectre, Meltdown, etc mitigations off-

Octane Score: 12341 (mitigations=off, firefox)
Octane Score: 12602 (mitigations=off, firefox)
Octane Score: 28102 (mitigations=off, chrome)
Octane Score: 28221 (mitigations=off, chrome)

🥳 Running at 110% of normal capacity sounds pretty good.

What about something closer to what I care about, like GUI interactivity? I kind of flailed around a bit on this, trying to find something that measured jank specifically, and came up short. There is, however, good ‘ol GtkPerf, which at least measures something close to what I care about. Fullscreen runs stabilized at around 8.9 seconds with mitigations on and 8.7 seconds with mitigations off. Is that an improvement? Is it good we can draw rubber ducks slightly faster?