News for hackers. Stuff that matters.

A comment on MDS: Microarchitectural Data Sampling side-channel vulnerabilities in Intel CPUs. Parent comment

Re:MDS: Microarchitectural Data Sampling side-channel vulner... by pertymcpert on Wednesday May 15, 2019 @12:30AM (#19916421)
I think you’re misunderstanding what HT is. It’s not true parallelism, it’s just hiding latency by providing some extra superscalar parallelism. You can’t expect it to give you actual linear improvements in performance because it’s just an illusion.
[ Parent | on HN ]
Re:MDS: Microarchitectural Data Sampling side-channel vulner... by beagle3 on Wednesday May 15, 2019 @01:41AM (#19916723)
I understand that very well. But non of the standard tools that manage CPU understand that, and most people don't either.

If I had a nickel for every time I had to explain why "You are at 50% CPU now, but you can't actually run twice as many processes on this machine and get the same runtime", I'd be able to buy a large frapuccino or two at starbucks.

Perhaps I'm uninformed though - is there a tool like htop, which would give me an idea of how close am I to maxing out a CPU?

[ Parent | on HN ]
Re:MDS: Microarchitectural Data Sampling side-channel vulner... by pertymcpert on Friday May 17, 2019 @12:43AM (#19936364)
No there isn’t. But if you understand it I don’t get why you think 20% isn’t a good performance boost, especially considering the rate of return for power and area in silicon.
[ Parent | on HN ]
Re:MDS: Microarchitectural Data Sampling side-channel vulner... by beagle3 on Friday May 17, 2019 @07:43AM (#19938568)
Because many people believe it is a 100% improvement, plan/budget accordingly, and then look for help.

As far as silicon/power it is nice, but IIRC (I am not involved in purchasing anymore) it used to cost over 50% in USD for those 20% in performance when you non-HT parts were common.

[ Parent | on HN ]
Re:MDS: Microarchitectural Data Sampling side-channel vulner... by pertymcpert on Friday May 17, 2019 @07:19PM (#19944504)
What a strange way to measure the benefits of a performance optimization: "how people will perceive it and then ask me for help".
[ Parent | on HN ]
Re:MDS: Microarchitectural Data Sampling side-channel vulner... by beagle3 on Saturday May 18, 2019 @01:57PM (#19948742)
You ignored the price issue, which was measurable and real, but also:

It (used to be) my job. Does "because people fall for deceptive marketing, waste money, and then waste my time trying to salvage their reputation" sound better?

[ Parent | on HN ]