The Combined Impact Of Retpoline + KPTI On Ubuntu Linux

[Michael]

What about AMD, how Retpoline patches impact performance?

Was benchmarked yesterday with Retpoline on Intel and AMD: https://www.phoronix.com/scan.php?pa...nchmarks&num=1

[Kayote]

this is laughable all the i7's have been turned into FX's. If I was an intel owner I would request my money back. I might as well do it with Ryzen if they can't keep their word of not crippling it as well.

[tomtomme]

this is laughable all the i7's have been turned into FX's. If I was an intel owner I would request my money back. I might as well do it with Ryzen if they can't keep their word of not crippling it as well.

AMD FX is not affected? Did anyone benchmark?

[DerCaveman]

Was benchmarked yesterday with Retpoline on Intel and AMD: https://www.phoronix.com/scan.php?pa...nchmarks&num=1

Yes, but it gets interesting comparing AMD + microcode (Retpoline only) against Intel + microcode (Retpoline + KPTI)

[fhuberts]

Yes, but it gets interesting comparing AMD + microcode (Retpoline only) against Intel + microcode (Retpoline + KPTI)

That is because AMD does not need KPTI

[blackshard]

Yes, but it gets interesting comparing AMD + microcode (Retpoline only) against Intel + microcode (Retpoline + KPTI)

That's the point. As long as Meltdown affects only Intel products, benchmarking AMD products with KPTI is like driving a car with the handbrake on.

[eva2000]

Thanks Michael for the benchmarks especially Apache and Nginx benchmarks which I am interested in. That 21-26% impact for Nginx is huge. I tested my Nginx build on CentOS 7.4 with updated Kernel with KPTI only and saw around 5.5% impact with Siege benchmark https://community.centminmod.com/thr...e-fixes.13694/ on i7 4790K which doesn't have microcode updates yet though.

[Slartifartblast]

That's the point. As long as Meltdown affects only Intel products, benchmarking AMD products with KPTI is like driving a car with the handbrake on.

Poor analogy, more like the "fix" VW had to apply to diesel engines for fiddling their emissions test which impacted performance.

[bridgman]

Poor analogy, more like the "fix" VW had to apply to diesel engines for fiddling their emissions test.

??? More like driving a non-fiddled vehicle from another mfg but patching in the performance-impacting VW changes even though they are not needed.

Actually given the specifics of the emissions "fix" the analogy might be beyond saving

[oleyska]

??? More like driving a non-fiddled vehicle from another mfg but patching in the performance-impacting VW changes even though they are not needed.

Actually given the specifics of the emissions "fix" the analogy might be beyond saving

The emissions was largely fixed with more accurate air reading to the ecm to have better fueling so it was trivial fix without much negative impact.
meltdown has negative impact :P