On Fri, Jun 14, 2024 at 06:28:00PM -0700, John Hubbard wrote: > On 6/14/24 6:24 PM, Boqun Feng wrote: > > On Fri, Jun 14, 2024 at 06:03:37PM -0700, John Hubbard wrote: > > > On 6/14/24 2:59 AM, Miguel Ojeda wrote: > > > > On Thu, Jun 13, 2024 at 9:05 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote: > > > > > > > > > > Does this make sense? > > > > > > > > Implementation-wise, if you think it is simpler or more clear/elegant > > > > to have the extra lower level layer, then that sounds fine. > > > > > > > > However, I was mainly talking about what we would eventually expose to > > > > users, i.e. do we want to provide `Atomic<T>` to begin with? If yes, > > > > then we could make the lower layer private already. > > > > > > > > We can defer that extra layer/work if needed even if we go for > > > > `Atomic<T>`, but it would be nice to understand if we have consensus > > > > for an eventual user-facing API, or if someone has any other opinion > > > > or concerns on one vs. the other. > > > > > > Well, here's one: > > > > > > The reason that we have things like atomic64_read() in the C code is > > > because C doesn't have generics. > > > > > > In Rust, we should simply move directly to Atomic<T>, as there are, > > > after all, associated benefits. And it's very easy to see the connection > > > > What are the associated benefits you are referring to? Rust std doesn't > > use Atomic<T>, that somewhat proves that we don't need it. > Just the stock things that a generic provides: less duplicated code, It's still a bit handwavy, sorry. Admittedly, I haven't looked into too much Rust concurrent code, maybe it's even true for C code ;-) So I took a look at the crate that Gary mentioned (the one provides generic atomic APIs): https://crates.io/crates/atomic there's a "Dependent" tab where you can see the other crates that depends on it. With a quick look, I haven't found any Rust concurrent project I'm aware of (no crossbeam, no tokio, no futures). On the other hand, there is a non-generic based atomic library: https://crates.io/crates/portable-atomic which has more projects depend on it, and there are some Rust concurrent projects that I'm aware of: futures, async-task etc. Note that people can get the non-generic based atomic API from Rust std library, and the "portable-atomic" crate is only 2-year old, while "atomic" crate is 8-year old. More interestingly, the same author of "atomic" crate, who is an expert in concurrent areas, has another project (there are a lot projects from the author, but this is the one I'm mostly aware of) "parking_lot", which "provides implementations of Mutex, RwLock, Condvar and Once that are smaller, faster and more flexible than those in the Rust standard library, as well as a ReentrantMutex type which supports recursive locking.", and it doesn't use the "atomic" crate either. These data could mean nothing, there are multiple reasons affecting the popularity of a library. But all the above seems to suggests that you don't really need generic on atomic, at least for a lot of meaningful concurent code. So if we were to make a decision right now, I don't see that generic atomics are winning. Of course, as I said previously, we can always add them if we have learned more and have the consensus. (Don't make me wrong, I love generic in general, I just want to avoid the "I have a generic hammer and everything looks like generic nails" situation.) Regards, Boqun > automatic support for future types (although here it's really just > integer types we care about of course). > > > thanks, > -- > John Hubbard > NVIDIA >
