it: run tests in parallel

src/utils/num_cpus.rs

@@ -0,0 +1,21 @@
+use {
+    crate::utils::oserror::OsError,
+    smallvec::{smallvec_inline, SmallVec},
+    uapi::{c, Errno},
+};
+
+#[allow(dead_code)]
+pub fn num_cpus() -> Result<u32, OsError> {
+    let mut buf: SmallVec<[usize; 32]> = smallvec_inline![0; 32];
+    loop {
+        match uapi::sched_getaffinity(0, &mut buf) {
+            Ok(_) => return Ok(count(&buf)),
+            Err(Errno(c::EINVAL)) => buf.extend_from_slice(&[0; 32][..]),
+            Err(e) => return Err(e.into()),
+        }
+    }
+}
+
+fn count(buf: &[usize]) -> u32 {
+    buf.iter().copied().map(|n| n.count_ones()).sum()
+}