chore: replace num_cpu with available_parallelism

Signed-off-by: tison <[email protected]>

Author: tisonkun

futures-executor/Cargo.toml

@@ -13,13 +13,12 @@ Executors for asynchronous tasks based on the futures-rs library.
 [features]
 default = ["std"]
 std = ["futures-core/std", "futures-task/std", "futures-util/std"]
-thread-pool = ["std", "num_cpus"]
+thread-pool = ["std"]
 
 [dependencies]
 futures-core = { path = "../futures-core", version = "=1.0.0-alpha.0", default-features = false }
 futures-task = { path = "../futures-task", version = "=0.4.0-alpha.0", default-features = false }
 futures-util = { path = "../futures-util", version = "=0.4.0-alpha.0", default-features = false }
-num_cpus = { version = "1.8.0", optional = true }
 
 [dev-dependencies]
 futures = { path = "../futures", features = ["thread-pool"] }

futures-executor/src/thread_pool.rs

@@ -6,7 +6,6 @@ use futures_task::{waker_ref, ArcWake};
 use futures_task::{FutureObj, Spawn, SpawnError};
 use futures_util::future::FutureExt;
 use std::boxed::Box;
-use std::cmp;
 use std::fmt;
 use std::format;
 use std::io;
@@ -190,13 +189,8 @@ impl ThreadPoolBuilder {
     ///
     /// See the other methods on this type for details on the defaults.
     pub fn new() -> Self {
-        Self {
-            pool_size: cmp::max(1, num_cpus::get()),
-            stack_size: 0,
-            name_prefix: None,
-            after_start: None,
-            before_stop: None,
-        }
+        let pool_size = thread::available_parallelism().map_or(1, |p| p.get());
+        Self { pool_size, stack_size: 0, name_prefix: None, after_start: None, before_stop: None }
     }
 
     /// Set size of a future ThreadPool