Add cgroups support for Linux targets

.travis.yml

@@ -1,7 +1,9 @@
 language: rust
 rust: stable
-dist: trusty
+dist: xenial
 sudo: false
+notifications:
+  email: disabled
 
 cache: cargo
 
@@ -65,3 +67,15 @@ matrix:
     - env: TARGET=x86_64-unknown-netbsd
     # Emscripten
     - env: TARGET=asmjs-unknown-emscripten
+
+    # CGroups in Docker
+    - name: Docker CGroups
+      install:
+      script:
+      - docker build -f ci/cgroups/Dockerfile -t num-cpus-cgroups .
+      # Test without cgroups
+      - docker run -it -e NUM_CPUS_TEST_GET=2 num-cpus-cgroups
+      # Only 1 CPU
+      - docker run -it --cpus="1" -e NUM_CPUS_TEST_GET=1 num-cpus-cgroups
+      # 1.5 CPUs
+      - docker run -it --cpus="1.5" -e NUM_CPUS_TEST_GET=2 num-cpus-cgroups

ci/cgroups/Dockerfile

@@ -0,0 +1,9 @@
+FROM rust:1.40
+
+WORKDIR /usr/num_cpus
+
+COPY . .
+
+RUN cargo build
+
+CMD [ "cargo", "test", "--lib" ]

fixtures/cgroups/cgroups/ceil/cpu.cfs_period_us

@@ -0,0 +1,2 @@
+100000
+

fixtures/cgroups/cgroups/ceil/cpu.cfs_quota_us

@@ -0,0 +1,2 @@
+150000
+

fixtures/cgroups/cgroups/good/cpu.cfs_period_us

@@ -0,0 +1,2 @@
+100000
+

fixtures/cgroups/cgroups/good/cpu.cfs_quota_us

@@ -0,0 +1,2 @@
+600000
+

fixtures/cgroups/cgroups/zero-period/cpu.cfs_period_us

@@ -0,0 +1,2 @@
+0
+

fixtures/cgroups/cgroups/zero-period/cpu.cfs_quota_us

@@ -0,0 +1 @@
+600000

fixtures/cgroups/proc/cgroups/cgroup

@@ -0,0 +1,3 @@
+12:perf_event:/
+11:cpu,cpuacct:/
+3:devices:/user.slice

fixtures/cgroups/proc/cgroups/mountinfo

@@ -0,0 +1,8 @@
+1 0 8:1 / / rw,noatime shared:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=reordered
+2 1 0:1 / /dev rw,relatime shared:2 - devtmpfs udev rw,size=10240k,nr_inodes=16487629,mode=755
+3 1 0:2 / /proc rw,nosuid,nodev,noexec,relatime shared:3 - proc proc rw
+4 1 0:3 / /sys rw,nosuid,nodev,noexec,relatime shared:4 - sysfs sysfs rw
+5 4 0:4 / /sys/fs/cgroup ro,nosuid,nodev,noexec shared:5 - tmpfs tmpfs ro,mode=755
+6 5 0:5 / /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime shared:6 - cgroup cgroup rw,cpuset
+7 5 0:6 / /sys/fs/cgroup/cpu,cpuacct rw,nosuid,nodev,noexec,relatime shared:7 - cgroup cgroup rw,cpu,cpuacct
+8 5 0:7 / /sys/fs/cgroup/memory rw,nosuid,nodev,noexec,relatime shared:8 - cgroup cgroup rw,memory

src/lib.rs

@@ -37,6 +37,11 @@ extern crate libc;
 #[cfg(target_os = "hermit")]
 extern crate hermit_abi;
 
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(target_os = "linux")]
+use linux::{get_num_cpus, get_num_physical_cpus};
+
 /// Returns the number of available CPUs of the current system.
 ///
 /// This function will get the number of logical cores. Sometimes this is different from the number
@@ -55,11 +60,14 @@ extern crate hermit_abi;
 ///
 /// # Note
 ///
-/// This will check [sched affinity] on Linux, showing a lower number of CPUs if the current 
-/// thread does not have access to all the computer's CPUs. 
+/// This will check [sched affinity] on Linux, showing a lower number of CPUs if the current
+/// thread does not have access to all the computer's CPUs.
+///
+/// This will also check [cgroups], frequently used in containers to constrain CPU usage.
 ///
 /// [smt]: https://en.wikipedia.org/wiki/Simultaneous_multithreading
 /// [sched affinity]: http://www.gnu.org/software/libc/manual/html_node/CPU-Affinity.html
+/// [cgroups]: https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
 #[inline]
 pub fn get() -> usize {
     get_num_cpus()
@@ -189,56 +197,6 @@ fn get_num_physical_cpus_windows() -> Option<usize> {
     }
 }
 
-#[cfg(target_os = "linux")]
-fn get_num_physical_cpus() -> usize {
-    use std::collections::HashMap;
-    use std::fs::File;
-    use std::io::BufRead;
-    use std::io::BufReader;
-
-    let file = match File::open("/proc/cpuinfo") {
-        Ok(val) => val,
-        Err(_) => return get_num_cpus(),
-    };
-    let reader = BufReader::new(file);
-    let mut map = HashMap::new();
-    let mut physid: u32 = 0;
-    let mut cores: usize = 0;
-    let mut chgcount = 0;
-    for line in reader.lines().filter_map(|result| result.ok()) {
-        let mut it = line.split(':');
-        let (key, value) = match (it.next(), it.next()) {
-            (Some(key), Some(value)) => (key.trim(), value.trim()),
-            _ => continue,
-        };
-        if key == "physical id" {
-            match value.parse() {
-                Ok(val) => physid = val,
-                Err(_) => break,
-            };
-            chgcount += 1;
-        }
-        if key == "cpu cores" {
-            match value.parse() {
-                Ok(val) => cores = val,
-                Err(_) => break,
-            };
-            chgcount += 1;
-        }
-        if chgcount == 2 {
-            map.insert(physid, cores);
-            chgcount = 0;
-        }
-    }
-    let count = map.into_iter().fold(0, |acc, (_, cores)| acc + cores);
-
-    if count == 0 {
-        get_num_cpus()
-    } else {
-        count
-    }
-}
-
 #[cfg(windows)]
 fn get_num_cpus() -> usize {
     #[repr(C)]
@@ -366,27 +324,6 @@ fn get_num_physical_cpus() -> usize {
     cpus as usize
 }
 
-#[cfg(target_os = "linux")]
-fn get_num_cpus() -> usize {
-    let mut set:  libc::cpu_set_t = unsafe { std::mem::zeroed() };
-    if unsafe { libc::sched_getaffinity(0, std::mem::size_of::<libc::cpu_set_t>(), &mut set) } == 0 {
-        let mut count: u32 = 0;
-        for i in 0..libc::CPU_SETSIZE as usize {
-            if unsafe { libc::CPU_ISSET(i, &set) } {
-                count += 1
-            }
-        }
-        count as usize
-    } else {
-        let cpus = unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) };
-        if cpus < 1 {
-            1
-        } else {
-            cpus as usize
-        }
-    }
-}
-
 #[cfg(any(
     target_os = "nacl",
     target_os = "macos",