This nigh-useless blurb links to a Youtube video: <a href="https://youtu.be/QkcBASKLyeU" rel="nofollow">https://youtu.be/QkcBASKLyeU</a>
To save you the time of watching the video: Spectre / Meltdown mitigations (page table isolation) cause execution inefficiency because of TLB cache misses.
So first of all: the lightning talk is certainly "worth it". Brendan Gregg is very knowledgeable and I can certainly recommend watching the talk. Its a good overview into the mindset of low-level optimization.<p>However, the core premise, the "headline" if you will of this talk, is utterly wrong. I get it: the headline needs to be a bit provocative to draw eyes, but its closer to "clickbait" than a good title of the talk.<p>The TL;DR of the talk is: Spectre/Meltdown caused a slowdown. But said slowdown is coming up as a ~+20% "CPU Utilization" under Linux performance measurement (ie: top or ps). This slowdown is because of a severe increase in TLB-misses.<p>Which... doesn't seem "wrong" to me. If the CPU is stalling because of TLB-buffer misses (kinda similar to an L2 cache miss or whatnot), then that's certainly CPU-time that is being wasted on something. Perhaps it isn't using power since the CPU is fully stalled, but the CPU is certainly "utilized" during that timeframe. Aside from hyperthreading: you can't really do something during the stall.<p>----------<p>Anyway, my criticism aside, the talk is certainly worthwhile to watch. And that's the important bit. So go ahead and watch the talk, even if I have a few pedantic qualms about the phrasing of the headline.<p>The real benefit of the talk is how Brendan Gregg diagnosed this performance problem, which eventually led to his conclusion about TLB-misses + Spectre. Demonstrating this skill and walking through a system to be able to draw this kind of conclusion is incredibly important.<p>I just don't... really like the title of the talk I guess. A rather minor concern all else considered.