2011/5/25 Rafael Ávila de Espíndola <respind...@mozilla.com>: >> Of arguing that the absence of data motivates a particular assumption. >> In this case it has to do with yield checking (which, incidentally, we >> do have some data on from the work in other JITs, and it's seldom a cost >> center). >> >> Elsewhere you seem to be frustrated that in the absence of data to the >> contrary, I'm promoting the assumption that M:N (even if it runs 1:1 >> much of the time) is a safer default than mandatory-1:1. I can't say for >> certain which of those scenarios *will* need M:N and how badly it'll >> hurt to be without; but I feel like mandatory-1:1 will paint ourselves >> into a bunch of potential corners, as I tried to point out in the last >> email. So I'm arguing the M:N stance is safer to start. >> >> Or maybe you're not frustrated about that, or hadn't previously >> considered those scenarios, and I am just reading frustration into the >> argument. Did any of the points I raised in defense of *permitting* M:N >> operation sound reasonable? > > I still don't see where I made an accusation. If I did, sorry, it was not > the intention. > > I am a bit frustrated that in the absence of data we are selecting the more > expensive option which is also the more expensive to backtrack and following > the examples of the least successful languages. >
I'm somewhat unconvinced that spawning an OS thread for every task should be considered the less expensive option. Easier to do, yes, but that pariticular performance claim goes directly against my performance intution, and could use some substantiation, IMO. E.g. Haskell does M:N threads and it's much more efficient than OS threads. I'd link you some microbenchmarks from the shootout game but that website seems broken at the moment - IIRC on the benchmarks measuring concurrency overhead, Haskell's M:N threading beat pretty much everything else including C without breaking much of a sweat. So, my current "gut instinct" (in the absence of data) is to favour light weight tasks that map to (few) OS tasks, for performance reasons. You seem to oppose that on performance grounds. I'm not sure why our intuitions differ, but I don't think there's enough data to, at this point, position the 1:1 option as the more higher performance option. Did I miss some elaboration on why you think it is? -- Sebastian Sylvan _______________________________________________ Rust-dev mailing list Rust-dev@mozilla.org https://mail.mozilla.org/listinfo/rust-dev
