Add support for using a jobserver with Rayon #56946
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,156 @@ | ||
| use jobserver_crate::{Client, HelperThread, Acquired}; | ||
| use lazy_static::lazy_static; | ||
| use std::sync::{Condvar, Arc, Mutex}; | ||
| use std::mem; | ||
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||
| #[derive(Default)] | ||
| struct LockedProxyData { | ||
| /// The number of free thread tokens, this may include the implicit token given to the process | ||
| free: usize, | ||
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| /// The number of threads waiting for a token | ||
| waiters: usize, | ||
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| /// The number of tokens we requested from the server | ||
| requested: usize, | ||
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| /// Stored tokens which will be dropped when we no longer need them | ||
| tokens: Vec<Acquired>, | ||
| } | ||
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| impl LockedProxyData { | ||
| fn request_token(&mut self, thread: &Mutex<HelperThread>) { | ||
| self.requested += 1; | ||
| thread.lock().unwrap().request_token(); | ||
| } | ||
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| fn release_token(&mut self, cond_var: &Condvar) { | ||
| if self.waiters > 0 { | ||
| self.free += 1; | ||
| cond_var.notify_one(); | ||
| } else { | ||
| if self.tokens.is_empty() { | ||
| // We are returning the implicit token | ||
| self.free += 1; | ||
| } else { | ||
| // Return a real token to the server | ||
| self.tokens.pop().unwrap(); | ||
| } | ||
| } | ||
| } | ||
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| fn take_token(&mut self, thread: &Mutex<HelperThread>) -> bool { | ||
| if self.free > 0 { | ||
| self.free -= 1; | ||
| self.waiters -= 1; | ||
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||
| // We stole some token reqested by someone else | ||
| // Request another one | ||
| if self.requested + self.free < self.waiters { | ||
| self.request_token(thread); | ||
| } | ||
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| true | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
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| fn new_requested_token(&mut self, token: Acquired, cond_var: &Condvar) { | ||
| self.requested -= 1; | ||
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| // Does anything need this token? | ||
| if self.waiters > 0 { | ||
| self.free += 1; | ||
| self.tokens.push(token); | ||
| cond_var.notify_one(); | ||
| } else { | ||
| // Otherwise we'll just drop it | ||
| mem::drop(token); | ||
| } | ||
| } | ||
| } | ||
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| #[derive(Default)] | ||
| struct ProxyData { | ||
| lock: Mutex<LockedProxyData>, | ||
| cond_var: Condvar, | ||
| } | ||
|
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| /// A helper type which makes managing jobserver tokens easier. | ||
| /// It also allows you to treat the implicit token given to the process | ||
| /// in the same manner as requested tokens. | ||
| struct Proxy { | ||
| thread: Mutex<HelperThread>, | ||
| data: Arc<ProxyData>, | ||
| } | ||
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| lazy_static! { | ||
| // We can only call `from_env` once per process | ||
|
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| // Note that this is unsafe because it may misinterpret file descriptors | ||
| // on Unix as jobserver file descriptors. We hopefully execute this near | ||
| // the beginning of the process though to ensure we don't get false | ||
| // positives, or in other words we try to execute this before we open | ||
| // any file descriptors ourselves. | ||
| // | ||
| // Pick a "reasonable maximum" if we don't otherwise have | ||
| // a jobserver in our environment, capping out at 32 so we | ||
| // don't take everything down by hogging the process run queue. | ||
| // The fixed number is used to have deterministic compilation | ||
| // across machines. | ||
| // | ||
| // Also note that we stick this in a global because there could be | ||
| // multiple rustc instances in this process, and the jobserver is | ||
| // per-process. | ||
| static ref GLOBAL_CLIENT: Client = unsafe { | ||
|
There was a problem hiding this comment. This I feel like There was a problem hiding this comment. I don't think any of this is related to memory safety though. |
||
| Client::from_env().unwrap_or_else(|| { | ||
| Client::new(32).expect("failed to create jobserver") | ||
| }) | ||
| }; | ||
|
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| static ref GLOBAL_PROXY: Proxy = { | ||
|
There was a problem hiding this comment. There is no ordering dependency on when There was a problem hiding this comment.
|
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| let data = Arc::new(ProxyData::default()); | ||
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| Proxy { | ||
| data: data.clone(), | ||
| thread: Mutex::new(client().into_helper_thread(move |token| { | ||
| data.lock.lock().unwrap().new_requested_token(token.unwrap(), &data.cond_var); | ||
| }).unwrap()), | ||
| } | ||
| }; | ||
| } | ||
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| pub fn client() -> Client { | ||
| GLOBAL_CLIENT.clone() | ||
| } | ||
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| pub fn acquire_thread() { | ||
| GLOBAL_PROXY.acquire_token(); | ||
| } | ||
|
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| pub fn release_thread() { | ||
| GLOBAL_PROXY.release_token(); | ||
| } | ||
|
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| impl Proxy { | ||
| fn release_token(&self) { | ||
| self.data.lock.lock().unwrap().release_token(&self.data.cond_var); | ||
| } | ||
|
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| fn acquire_token(&self) { | ||
| let mut data = self.data.lock.lock().unwrap(); | ||
| data.waiters += 1; | ||
| if data.take_token(&self.thread) { | ||
| return; | ||
| } | ||
| // Request a token for us | ||
| data.request_token(&self.thread); | ||
| loop { | ||
| data = self.data.cond_var.wait(data).unwrap(); | ||
| if data.take_token(&self.thread) { | ||
| return; | ||
| } | ||
| } | ||
| } | ||
| } | ||
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