feat(spdk): allow SPDK tracing

Init SPDK tracing when `MayastorEnvironment.num_enties` is set to a
positive integer. This can be helpfull when developing new features.
Traces can be found in `/dev/shm` and have the pid or if not negative
the `MayastorEnvironment.shm_id` as a suffix.

Further information about traces and how to read the captured traces can
be found here: https://spdk.io/doc/nvmf_tgt_tracepoints.html

Signed-off-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>

io-engine/src/core/env.rs

@@ -44,6 +44,9 @@ use spdk_rs::{
         spdk_thread_lib_fini,
         spdk_thread_send_critical_msg,
         spdk_trace_cleanup,
+        spdk_trace_create_tpoint_group_mask,
+        spdk_trace_init,
+        spdk_trace_set_tpoints,
         SPDK_LOG_DEBUG,
         SPDK_LOG_INFO,
         SPDK_RPC_RUNTIME,
@@ -1020,6 +1023,40 @@ impl MayastorEnvironment {
         None
     }
 
+    fn init_spdk_tracing(&self) {
+        const MAX_GROUP_IDS: u32 = 16;
+        const NUM_THREADS: u32 = 1;
+        let cshm_name = if self.shm_id >= 0 {
+            CString::new(
+                format!("/{}_trace.{}", self.name, self.shm_id).as_str(),
+            )
+            .unwrap()
+        } else {
+            CString::new(
+                format!("/{}_trace.pid{}", self.name, std::process::id())
+                    .as_str(),
+            )
+            .unwrap()
+        };
+        unsafe {
+            if spdk_trace_init(cshm_name.as_ptr(), self.num_entries, NUM_THREADS) != 0 {
+                error!("SPDK tracing init error");
+            }
+        }
+        let tpoint_group_name = CString::new("all").unwrap();
+        let tpoint_group_mask = unsafe {
+            spdk_trace_create_tpoint_group_mask(tpoint_group_name.as_ptr())
+        };
+
+        for group_id in 0..MAX_GROUP_IDS {
+            if (tpoint_group_mask & (1 << group_id) as u64) > 0 {
+                unsafe {
+                    spdk_trace_set_tpoints(group_id, u64::MAX);
+                }
+            }
+        }
+    }
+
     /// initialize the core, call this before all else
     pub fn init(mut self) -> Self {
         // setup the logger as soon as possible
@@ -1088,6 +1125,11 @@ impl MayastorEnvironment {
         // ensure we are within the context of a spdk thread from here
         Mthread::primary().set_current();
 
+        // To enable SPDK tracing set self.num_entries (eg. to 32768).
+        if self.num_entries > 0 {
+            self.init_spdk_tracing();
+        }
+
         Reactor::block_on(async {
             let (sender, receiver) = oneshot::channel::<bool>();