can we take the good things from libfringe and put them into may/generator

[alkis]

https://github.com/edef1c/libfringe

This crate has rather nice approach to switching contexts:

• instead of saving all callee registers it issues asm to denote they are clobbered. Then the compiler saves only the registers that need saving
• at least on unix it stitches back the stack so stack traces look legible
• performance seems unparalleled: 3ns per context switch (granted only when a few registers are saved)

[Xudong-Huang]

That's an awesome good idea! Currently the context switch would cost about 30ns on unix, this would improve the performance significantly. We need to integrate it in the generator library. I also want grab some good things from parking_lot about the thread wakeup, but this should be another issue.

[Xudong-Huang]

I think this is done in the nightly build. just include following config in your application's Cargo.toml

[replace]
"generator:0.6.5" = { git = "https://github.com/Xudong-Huang/generator-rs.git", branch = "libfringe" }

this should replace all the dependent generator library by using the libfringe branch. Though the generator context switch is improved 2 times faster than the master branch, but it's not the critical bottleneck for coroutine tasks, so I didn't see much improvement for the heavy io test.

[Xudong-Huang]

for the stable branch use this feature we need to wait rust asm feature got stabled.