rz30221 (u/rz30221) - Readit News

rz30221 commented on Is Silicon Valley’s golden era coming to an end? theguardian.com/business/... · Posted by u/elsewhen

metadat · 3 years ago

Snapchat doesn't even have a Bay Area office. Also, since when is bracing for economic realities a sign that the entire organism is dying? It doesn't, this article is simply capitalizing on FUD.

As long as Sandhill road remains fully occupied by VCs, the gravy train will continue.

rz30221 · 3 years ago

Snapchat may not, but many of these companies have Bay Area Headquarters. I didn't bother to count but it's a lot. https://companiesmarketcap.com/software/largest-software-com...

That doesn't mean the good years are going to last forever but I think we've got a bit of time before the end.

rz30221 commented on How quickly do CPUs change clock speeds? chipsandcheese.com/2022/0... · Posted by u/zdw

clamchowder · 3 years ago

Yeah, didn't want to start an article with a five paragraph essay especially when wordpress pagination doesn't work, so I can't get an Anandtech style multi-page article up.

And yep. You can even run a CPU at full clock all the time, meaning you will never observe a clock transition time. Cloud providers seem to do that.

rz30221 · 3 years ago

I actually liked the article and I think the first image is really informative.

I guess my point is the "clock frequency ramp time" is really due to the interplay of a bunch of different control systems, some in the OS and some not. And when those systems get mixed together, in a somewhat uncontrolled way (which is the case for most PCs), a huge amount of variability is the result and that's what the article did a good job quantifying but IMHO didn't make clear.

But at the time scales in your plots "how quickly CPUs change clock speeds" is basically an implementation choice.

Just my $0.02

rz30221 commented on How quickly do CPUs change clock speeds? chipsandcheese.com/2022/0... · Posted by u/zdw

clamchowder · 3 years ago

> The Linux CPU frequency governor literally uses it as part of the algorithm for calculating its sampling rate

Yes, the governor can play a role. It's visible to the user, which is the point. Also, the ondemand governor is actually irrelevant to the article as the S821 and S670 used the interactive and schedutil governors respectively, and the i5-6600K was using speed shift.

I think we're disagreeing because I really don't care about how fast a CPU could pull off frequency transitions if it's never observable to users. I'm looking at how it's observable to user programs, and how fast the transition happens in practice.

> Processor still performs periodic sampling...

Same as the above, that's not the point of the article. I'm not measuring "what could theoretically happen if you ignore half the steps involved in a frequency transition even though a user realistically cannot avoid them without serious downsides" (like artificially holding the idle voltage high and drawing more idle power, as in the Piledriver example)

> In any case, a multi-millisecond delay in switching frequency isn't because the processor is waiting for the voltage to increase.

Yes, there are other factors involved besides the voltage increase. I never said it was the only factor, and did mention speed shift taking OS transition commands out of the picture (implying that requiring OS commands does introduce a delay in CPUs without such a feature).

If you want to test how fast a CPU can clock up, without influence from OS/processor polling, please do so and publish your results along with your methodology. I think it'd be interesting to see.

rz30221 · 3 years ago

I read the article in full, and the data & information was interesting, but I have to say a lot of the points you're making in the comments now was not clear from the article text alone.

Another important point is you're measuring the default behavior of the various control systems. One can change that which would allow the user to observe something else.

rz30221 commented on The movie Hackers was released 27 years ago blog.adafruit.com/2022/09... · Posted by u/Napsty

ramesh31 · 3 years ago

>Between Hackers, Masters of Doom, and other rad 90s hacker-coder media, software development really seemed like a much more awesome career than it turned out to be.

I think it comes down to the fact that our industry has become rigid and beholden to the university education system. John Carmack and John Romero were both college dropouts. Their stories would probably be impossible today. What we have now is a world of people coloring between the lines and going straight from one set of rules to another. There truly is no more punk rock left in tech.

rz30221 · 3 years ago

Industry, for the most part, needs predictability and scale for it to function well. It's very difficult to accomplish that without at least some rigidity.

Punk rock is small by definition. Once it becomes large it changes to mainstream.

rz30221 commented on The movie Hackers was released 27 years ago blog.adafruit.com/2022/09... · Posted by u/Napsty

derwiki · 3 years ago

Aside from crypto startups, could you share an example?

rz30221 · 3 years ago

The presenters in Defcon seem like they enjoy what they do, for example.

rz30221 commented on Ask HN: How would you design a Modern Operating System in 2022? · Posted by u/Decabytes

arghnoname · 3 years ago

Academic research on this topic is limited, but ongoing. You'd want to look at OSDI and SOSP conferences--they're both OS conferences, even if only a few papers each year are actually about OS design. Lots of ideas there though.

HotOS is a workshop, but tends to be more creative and daring since it's just top researchers sharing their thoughts on OS design.

Off the top of my head in recent years you've had unikernels (e.g., mirageOS), barrel fish (multikernel), omnix (for dealing with lots of asics and other accelerators), and lots of modifications to existing OS design, like a ring-io like asynchronous system call mechanism (flexSC), systems for adding new abstractions off of modern hardware, like Dune, and of course ongoing work on microkernels, most significantly (and commercially), seL4.

Older research is still relevant. Capability systems and exokernels influence the above work and the original well-spring is still worth visiting.

Basically though, what you want to address are some of the following:

* Higher security requirements. Multitenancy is a given. Giant code blobs running without restriction in the same security domain (i.e., monolithic kernels) is a bad idea.

* Greater hardware support for differing security modes (virtualization, enclaves, trust zones, CHERI)

* Advances in compiler/language research and techniques for low-cost policy enforcement at the language level (to at least some degree), allowing for 'uploading' code into ring0 . Rust is the most popular example, but even just the eBPF trend is an example of this.

* Heterogenous hardware. How does the kernel handle differing cores with different performance characteristics, power requirements, capabilities, and even different ISAs? This is happening. Should the OS expose better primitives for ASICS and other accelerators?

* Cloud computing. Many big money work loads run under someone else's control with a hypervisor. This brings up attestation, but also raises the question if you're running a single application under a hypervisor (itself basically a microkernel), what do you need a full fledged kernel for? Similar to userland duplication with containers. Unikernels are one such response, but it's something that should be addressed.

All in all, pretty much anything I see in industry (conceptually) is trialed out in one form or another in academia many years in advance. Industry is theoretically where the really hard work of making it practical happens, but sadly this seems to very rarely happens.

rz30221 · 3 years ago

> and even different ISAs

That is super interesting. I did some Googling but couldn't find an example of one. Do you know of an example of an OS that can handle different ISAs? I suppose in some sense an accelerator can be considered a "core with a different ISA" but I interpreted the statement as basically supporting multiple ABIs in parallel. Maybe I overreached?