Is It Worthwhile Running Intel Alder Lake With mitigations=off?

[mr_marmalade]

nevermind

[avem]

Source? From my limited pts/osbench benchmarks, practically zero effect disabling mitigations on Zen 3 (5800X). Might have been true before, but no longer true with latest microcodes/patches.

Phoronix post

Openbenchmarking link

Your limited right.

Here's Michael's own most recent data.

Almost 7% for 5600X which is not something to be trifled with.

[perpetually high]

December 2020 is far from recent. That’s exactly one year ago. Lots has changed. We’ll have to get a refresh of these benchmarks. Regardless, thanks for following up avem

[Teggs]

Looks like Intel has done a spectacular job of addressing performance regressions related to the use of mitigations. Kudos!

What evidence do you have for this? In this case, Alder Lake has a host of mitigations baked in, and we have no theoretical 'clean' silicon to test against to see how efficient the mitigations are.

[darkcoder]

With due respect to Michael, imo is more important to know if the mitigations are actually still needed, considering is a new architecture and very likely mitigations are already in place on the design.

[bug77]

Is it worth running the iGPU with DDR4 or DDR5 memory, please tell us Mike.

The IGP is fine for desktop tasks and inadequate for gaming with either RAM type. You don't need benchmarks to tell you that.

[bug77]

Thanks for working out that math on that, I was curious myself lol. And yeah I didn't mean to say "zero effect" on Zen 3 since I did see *a* difference but not as much as Alder Lake, which is really impressive by Intel.

The numbers thrown around in comments are deceptive. Mitigations' impact has always been highly workload dependent. Most scenarios unaffected, select few hit rather significantly. Averages tell squat in this context.

[NobodyXu]

With due respect to Michael, imo is more important to know if the mitigations are actually still needed, considering is a new architecture and very likely mitigations are already in place on the design.

Maybe it would be a good idea to disable these migrations by tinkering with the CPU microcode?

For the old CPU we can downgrade microcode, but for the new ones… perhaps it can be disabled in BIOS?

[Alex/AT]

Given 'mitigations=off' even gives worse performance at places while it definitely should not by design, I start to suspect another cheat buried somewhere in the new hardware. Just wonder how many time will pass before it's discovered and exploited.

Looks like Intel has done a spectacular job of addressing performance regressions related to the use of mitigations

Yeah indeed, looks the same to me. Last time a similar spectacular 'addressing performance' job skipping privilege checks resulted in Meltdown L1 timing exploit relying on out-of-privilege access being discovered, so can't be anything but sceptical here about the new findings.

[avem]

What evidence do you have for this? In this case, Alder Lake has a host of mitigations baked in, and we have no theoretical 'clean' silicon to test against to see how efficient the mitigations are.

Are you sane? Previous gen Intel CPUs show quite a performance loss of up to 90% in certain tasks, while for ADL it's below 1%. What further evidence do you need other than benchmarks?