Very cool! Also, huh interesting. I’ve used rdtsc to measure cycle diffs but had no idea its execution takes that long. Is that common across architectures?
This author also has other things like: A compiler that emits only `mov` instructions and another compiler that deliberately messes with the control flow so that, if disassembled, common debuggers will draw symbols like skulls or threats. https://github.com/xoreaxeaxeax/repsych
It is literally impossible to respond to input in 10ms on most platforms, for various reasons. The USB input lag of 12-30ms and the 60Hz refresh rate of most monitors being just the first two.
There’s definitely strategies here; A lot of the floating point operations use subnormals, and a lot of the worst instructions are slowed down by really, really fucking with MMIO.
It'd be really interesting to see whether the winning (losing?) instructions/strategies would be different on other architectures. At least right now the top spot (`fxrstor64` on MMIO, starve PCIe) seems relatively architecture-independent, but maybe something about MMIO ordering rules on e.g. POWER would be different enough to change that -- or perhaps open up new avenues?
I wonder what the actual limit on this `fxrstor64` is right now. If you can stall the PCIe bus for that long, then why not indefinitely? Certainly there's no forward progress guarantee here.
Nop should be #1, because it is infinitely slow for what it does. ;)
It increments rip by one.
Strategy: nop does nothing. It opens the leaderboard accordingly.
Score: 1 cycles Time: 0 nanoseconds
Related, and linked in the readme: https://github.com/xoreaxeaxeax/smiiiiiiiiiiiiiiii (using the slow instructions to break SMI)
Very cool! Also, huh interesting. I’ve used rdtsc to measure cycle diffs but had no idea its execution takes that long. Is that common across architectures?
AFAIK it acts as some kind of execution barrier, to give meaningful timing.
Isn't that rdtscp ( https://www.felixcloutier.com/x86/rdtscp )?
This author also has other things like: A compiler that emits only `mov` instructions and another compiler that deliberately messes with the control flow so that, if disassembled, common debuggers will draw symbols like skulls or threats. https://github.com/xoreaxeaxeax/repsych
He also bruteforced the entire opcode space to find undocumented instructions (sandsifter).
what im seeing from this chart is that we should be using the nop instruction for everything
Well the best code is no code. Nop could be second best though.
Instructions unclear. Set the NX bit to ensure no code, and got a general protection fault.
Oh wow, glad to see Chris Domas active online again!
A great resource for any performance deoptimization.
It’s crazy how computers still seem to get perceivably slow every few years, given how many instructions can be executed in 1ms. Shameful, even..
What’s that law called about programmers wasting all the compute on abstraction?
Andy and Bill's Law
The new windows notepad is a disgrace
The OS should do less not more
Wirth's Law I believe.
And remember to call him by name, not by value!
Huh? A millisecond is an eternity!
I remember reading once somewhere:
If some app responds in 10ms or less, it is INTERACTIVE.
makes you think.
It is literally impossible to respond to input in 10ms on most platforms, for various reasons. The USB input lag of 12-30ms and the 60Hz refresh rate of most monitors being just the first two.
There’s definitely strategies here; A lot of the floating point operations use subnormals, and a lot of the worst instructions are slowed down by really, really fucking with MMIO.
It'd be really interesting to see whether the winning (losing?) instructions/strategies would be different on other architectures. At least right now the top spot (`fxrstor64` on MMIO, starve PCIe) seems relatively architecture-independent, but maybe something about MMIO ordering rules on e.g. POWER would be different enough to change that -- or perhaps open up new avenues?
I wonder what the actual limit on this `fxrstor64` is right now. If you can stall the PCIe bus for that long, then why not indefinitely? Certainly there's no forward progress guarantee here.