FreeBSD Scheduling on Hybrid CPUs(wiki.freebsd.org) |
FreeBSD Scheduling on Hybrid CPUs(wiki.freebsd.org) |
So, when powered by AC power, schedule everything on P cores when possible, schedule processes that eat a lot of CPU on P cores, same for any process with a negative nice value.
When powered by a battery, schedule anything with non-negative nice value on E cores, keep one P core up for real-time tasks, and for nice-below-zero tasks.
These are two extremes, but I suppose that the idea is understandable.
Even when plugged in, you may have thermal limitations. P cores will chew through your power budget more aggressively than E cores. For latency-sensitive workloads you do want to emphasize the P cores, but when throughput is the goal you'll usually be better off not ignoring the E cores, and not trying to run the P cores at high frequency where they're much less efficient. Intel started adding E cores to consumer chips in large part so they could score better on throughput-oriented multithreaded benchmarks like Cinebench; they're decent at compiling code, too, but you'll still want the P core for the linker.
Sometime I feel like that is undesirable. It may make system consume more power, thus more heat output and louder.
It'd be cool if tasks told you about their workload in terms of latency throughput, and cadence required (hello skipping audio when you compile hard).
https://developer.apple.com/library/archive/documentation/Pe...
If when the battery is full you make the right decisions your battery can last longer. However this isn't something you can do. You don't want a pop-up when your email program spawns a thread to check for new email - programs do this all the time and the system doesn't know if the thread itself will run for a few ms or for hours. In most cases the battery consumed by the popup will be more than the thread itself uses. You want the system to make the right decisions - but the right decision depends on your system and someone else with a difference CPU may need different decisions.
My bigger concern with the newer Intel CPUs are the crashes and reliability issues that were reported.
The AMD Bulldozers put a lot of new, untested ideas in to practice. Some of them paid off, while many did not, at least not in the short term. There were, however, many good ideas, and many of those lived on and helped make Ryzen what it is.
Over time, Bulldozer performance has matched and exceeded contemporary Intel performance, both because compiler optimizations have made better use of the CPU and because of the slowdowns from Spectre / Meltdown affecting Intel much more than AMD. I still run an FX-8150 server and have compared it with an Intel 2600K system in many tasks.
Do we think that Intel is going to use their current shitshow to make a golden age of Intel CPUs, like how Bulldozer led to Ryzen? I personally don't think so. They've put all their cheap tricks in to their CPUs, tricks which require huge slowdowns when flaws are found, and unless / until they start caring about actually doing things correctly rather than playing fast and loose with hundreds of watts, they'll keep trying to game the benchmarks, will keep having flaws and problems, and will keep losing market share.
Really? I just bought one:
https://www.intel.com/content/www/us/en/products/sku/236786/...
That bit actually still applies. Intel may have branded the 14100F as Raptor Lake, but it is almost certainly Alder Lake silicon, just a higher speed bin of the 12100F.
See https://www.intel.com/content/www/us/en/products/compare.htm... and note how none of them get the higher DRAM frequency support or larger L2 caches characteristic of Raptor Lake silicon.
For CPU's, those two types of efficiency are closely related. Omitted transistors (in an E core design) neither take up die space, nor consume power. And CPU cooling systems are ultimately measured by how many watts of heat they can remove from each unit of die area - so fewer watts from a smaller core. (That's at a given temperature difference, etc. But your die will die if any part of it gets too hot. And revving up the CPU cooling fan is generally not preferred.)
They are a bit expensive but I wouldn't expect them to drop these skews in the long term for HPC & compute bound workloads. My guess is that diamond rapids will also have some P-skews and maybe AP skews.
Only way to stop laptop getting crazy hot and fans meaningfully reducing pressure on desk of laptop...