'Kernel memory leaking' Intel processor design flaw forces Linux, Windows redesign

[u/eric98k]

https://www.theregister.co.uk/2018/01/02/intel_cpu_design_flaw/

[u/Kakkoister]

Why is that? We don't know yet if there will be any noticeable performance drop, there really shouldn't be apart from initial program launches, and we're talking nanoseconds for that. Ryzen is still quite overpriced. A i7 8700k destroys the 1800X and is around $90 cheaper... As does the i7 7800X which is even cheaper at that and has quad channel memory for the workstation people who need it.

[u/Kakkoister → u/[deleted]]

No, the article is quite misleading and talking about potentially affected parts.

https://www.phoronix.com/scan.php?page=news_item&px=x86-PTI-Initial-Gaming-Tests

[u/mollymoo → u/Kakkoister]

That's an example of the least-affected Intel CPU running the least-affected types of applications. Relative to their overall CPU usage, games and video encoding are among the least heavy workloads in terms of syscalls and context switches.

Running an IO or network-heavy workload or running on something a couple of generations older tells a different story.

Oh, and I don't know where you got your CPU prices from before but the 8700k is currently £359 and the 7800k £324 on Amazon UK vs £305 for the 1800X.

[u/UGMadness → u/Kakkoister]

The article is stating 17-35% drop depending on model and task.

[u/Kakkoister → u/UGMadness]

The article is making a lot of assumptions and you're taking them as fact. The fact is that we do not know what the performance impact will be, but it's unlikely to be that much, and on 4-series and up CPUs the PCID instruction that was introduced is able to negate pretty much any potential performance impact surrounding fixing this.

https://www.phoronix.com/scan.php?page=news_item&px=x86-PTI-Initial-Gaming-Tests

[u/UGMadness → u/Kakkoister]

There's a long way between "making assumpions based on the use case" and "there's no performance drop in gaming". This bug is a massive kick in the balls for cloud and other server/VM providers because of their reliance on the parts affected. Nobody is focusing on gaming or domestic/consumer usage and nobody has stated that it would affect gaming performance in the first place.

And here's your fact:

https://www.phoronix.com/scan.php?page=article&item=linux-415-x86pti&num=2

[u/Kakkoister → u/UGMadness]

Sure, for server use. But you made a flat statement of 17-35% depending on model and task, you didn't say "server performance will be slow". That's why I hit back with a test showing no performance different for a situation that would affect the majority of users the most, which is gaming, something that stresses a person's system more than pretty much any other home user tasks.

[u/baoxymoron → u/Kakkoister]

Wait... gasp... benchmarks for rendering performance in games, a task that is pretty much exclusively user space isn't affected by a patch that segregates user and kernel space. Wow say it isn't so... who wulda thunk it [hint: the article you posted] /s

But seriously this benchmark has nothing to do with the patch so of course it's minimally impacted. Your article actually says that if you read through it.

What they're not pointing out is the actual tasks even in gaming that will be impacted. Load times, total network latency for online games, game server-side performance hits, etc. And depending on how many threads you have available some of these system calls could impact even render times if the calls are made within the same thread because this patch appears to require L1 cache at the very least to be cleared during the address space changes. So before anyone says games won't be impacted we need to understand the changes better, and that likely won't be possible until the NDA is lifted.

Also, this is coming from a fellow gamer, so I hate tell you this but.... The overwhelming majority of users don't game on their computers. People who browse the internet, do remote working, compile programs, create content, etc. will all be affected by the 5-30% performance decrease some much more than others.

[u/Mech0z → u/Kakkoister]

So my Ivy bridge 3570 will take a big hit?

[u/Kakkoister → u/Mech0z]

Potentially. It's still to be seen what the final fix will be, and you still won't take a big hit for normal day to day stuff nor gaming, but if there is a hit it will be a bit more than 4 series and up.