Add support for memory.zswap.current

Summary: We want to collect memory.zswap.current so that we can easily debug & monitor rollout of the `memory.zswap.current` cgroup file

Reviewed By: dschatzberg, lnyng, brianc118

Differential Revision: D35581379

fbshipit-source-id: 81d1f50952ec9183023931cdd668ff4ba49904b3

2 files changed, 18 insertions, 0 deletions

diff --git a/below/cgroupfs/src/lib.rs b/below/cgroupfs/src/lib.rs
index f2ef3da6..672e6544 100644
--- a/below/cgroupfs/src/lib.rs
+++ b/below/cgroupfs/src/lib.rs
@@ -185,6 +185,12 @@ impl CgroupReader {
         self.read_singleline_stat_file("memory.swap.current")
     }
 
+    /// Read memory.zswap.current - returning current cgroup memory
+    /// zswap consumption in bytes
+    pub fn read_memory_zswap_current(&self) -> Result<u64> {
+        self.read_singleline_stat_file("memory.zswap.current")
+    }
+
     /// Read cpu.stat - returning assorted cpu consumption statistics
     pub fn read_cpu_stat(&self) -> Result<CpuStat> {
         CpuStat::read(&self)
diff --git a/below/cgroupfs/src/test.rs b/below/cgroupfs/src/test.rs
index d5ed41b5..b79943e3 100644
--- a/below/cgroupfs/src/test.rs
+++ b/below/cgroupfs/src/test.rs
@@ -135,6 +135,18 @@ fn test_memory_swap_current_success() {
 }
 
 #[test]
+fn test_memory_zswap_current_success() {
+    let cgroup = TestCgroup::new();
+    cgroup.create_file_with_content("memory.zswap.current", b"1234\n");
+
+    let cgroup_reader = cgroup.get_reader();
+    let val = cgroup_reader
+        .read_memory_zswap_current()
+        .expect("Failed to read memory.zswap.current");
+    assert_eq!(val, 1234);
+}
+
+#[test]
 fn test_memory_high_success() {
     let cgroup = TestCgroup::new();
     cgroup.create_file_with_content("memory.high", b"1234\n");