Replace hashmap for io_uring pending ops with static array

core/io/io_uring.rs

@@ -4,7 +4,6 @@ use log::{debug, trace};
 use rustix::fs::{self, FlockOperation, OFlags};
 use rustix::io_uring::iovec;
 use std::cell::RefCell;
-use std::collections::HashMap;
 use std::fmt;
 use std::io::ErrorKind;
 use std::os::fd::AsFd;
@@ -40,7 +39,7 @@ pub struct UringIO {
 struct WrappedIOUring {
     ring: io_uring::IoUring,
     pending_ops: usize,
-    pub pending: HashMap<u64, Rc<Completion>>,
+    pub pending: [Option<Rc<Completion>>; MAX_IOVECS as usize + 1],
     key: u64,
 }
 
@@ -63,7 +62,7 @@ impl UringIO {
             ring: WrappedIOUring {
                 ring,
                 pending_ops: 0,
-                pending: HashMap::new(),
+                pending: [const { None }; MAX_IOVECS as usize + 1],
                 key: 0,
             },
             iovecs: [iovec {
@@ -92,7 +91,7 @@ impl InnerUringIO {
 impl WrappedIOUring {
     fn submit_entry(&mut self, entry: &io_uring::squeue::Entry, c: Rc<Completion>) {
         trace!("submit_entry({:?})", entry);
-        self.pending.insert(entry.get_user_data(), c);
+        self.pending[entry.get_user_data() as usize] = Some(c);
         unsafe {
             self.ring
                 .submission()
@@ -124,6 +123,11 @@ impl WrappedIOUring {
 
     fn get_key(&mut self) -> u64 {
         self.key += 1;
+        if self.key == MAX_IOVECS as u64 {
+            let key = self.key;
+            self.key = 0;
+            return key;
+        }
         self.key
     }
 }
@@ -175,10 +179,11 @@ impl IO for UringIO {
                 )));
             }
             {
-                let c = ring.pending.get(&cqe.user_data()).unwrap().clone();
-                c.complete(cqe.result());
+                if let Some(c) = ring.pending[cqe.user_data() as usize].as_ref() {
+                    c.complete(cqe.result());
+                }
             }
-            ring.pending.remove(&cqe.user_data());
+            ring.pending[cqe.user_data() as usize] = None;
         }
         Ok(())
     }