From 997716c62d96467216031d7c0a770ffa81d8484d Mon Sep 17 00:00:00 2001
From: Haomai Wang <haomai@xsky.com>
Date: Thu, 7 Jan 2016 22:11:00 +0800
Subject: [PATCH] NVMEDevice: don't try to acquire lock always

Signed-off-by: Haomai Wang <haomai@xsky.com>
---
 src/os/bluestore/NVMEDevice.cc | 32 ++++++++++++++++++++++++++++----
 src/os/bluestore/NVMEDevice.h  |  1 +
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/os/bluestore/NVMEDevice.cc b/src/os/bluestore/NVMEDevice.cc
index 2bfefc328e0b0..7873a2f46b18d 100644
--- a/src/os/bluestore/NVMEDevice.cc
+++ b/src/os/bluestore/NVMEDevice.cc
@@ -287,6 +287,7 @@ NVMEDevice::NVMEDevice(aio_callback_t cb, void *cbpriv)
     : ctrlr(nullptr),
       ns(nullptr),
       aio_stop(false),
+      queue_empty(1),
       queue_lock("NVMEDevice::queue_lock"),
       aio_thread(this),
       inflight_ops(0),
@@ -334,7 +335,11 @@ void NVMEDevice::close()
 {
   dout(1) << __func__ << dendl;
 
-  aio_stop = true;
+  {
+    Mutex::Locker l(queue_lock);
+    aio_stop = true;
+    queue_cond.Signal();
+  }
   aio_thread.join();
   aio_stop = false;
   name.clear();
@@ -356,12 +361,17 @@ void NVMEDevice::_aio_thread()
   while (!aio_stop) {
     dout(40) << __func__ << " polling" << dendl;
     t = nullptr;
-    {
+    if (!queue_empty.read()) {
       Mutex::Locker l(queue_lock);
       if (!task_queue.empty()) {
         t = task_queue.front();
         task_queue.pop();
       }
+      queue_empty.inc();
+    } else if (!inflight_ops.read()) {
+      Mutex::Locker l(queue_lock);
+      if (queue_empty.read())
+        queue_cond.Wait();
     }
 
     if (t) {
@@ -397,8 +407,9 @@ void NVMEDevice::_aio_thread()
             t->return_code = r;
             Mutex::Locker l(t->ctx->lock);
             t->ctx->cond.Signal();
+          } else {
+            inflight_ops.inc();
           }
-          inflight_ops.inc();
           break;
         }
         case IOCommand::FLUSH_COMMAND:
@@ -410,8 +421,9 @@ void NVMEDevice::_aio_thread()
             t->return_code = r;
             Mutex::Locker l(t->ctx->lock);
             t->ctx->cond.Signal();
+          } else {
+            inflight_ops.inc();
           }
-          inflight_ops.inc();
           break;
         }
       }
@@ -452,6 +464,10 @@ int NVMEDevice::flush()
   {
     Mutex::Locker l(queue_lock);
     task_queue.push(t);
+    if (queue_empty.read()) {
+      queue_empty.dec();
+      queue_cond.Signal();
+    }
   }
   {
     Mutex::Locker l(ioc.lock);
@@ -476,6 +492,10 @@ void NVMEDevice::aio_submit(IOContext *ioc)
   Mutex::Locker l(queue_lock);
   // Only need to push the first entry
   task_queue.push(t);
+  if (queue_empty.read()) {
+    queue_empty.dec();
+    queue_cond.Signal();
+  }
 }
 
 int NVMEDevice::aio_write(
@@ -587,6 +607,10 @@ int NVMEDevice::read(uint64_t off, uint64_t len, bufferlist *pbl,
   {
     Mutex::Locker l(queue_lock);
     task_queue.push(t);
+    if (queue_empty.read()) {
+      queue_empty.dec();
+      queue_cond.Signal();
+    }
   }
 
   {
diff --git a/src/os/bluestore/NVMEDevice.h b/src/os/bluestore/NVMEDevice.h
index af99999f1cba1..c83fbaec8e0b5 100644
--- a/src/os/bluestore/NVMEDevice.h
+++ b/src/os/bluestore/NVMEDevice.h
@@ -72,6 +72,7 @@ class NVMEDevice : public BlockDevice {
   bool aio_stop;
   bufferptr zeros;
 
+  atomic_t queue_empty;
   Mutex queue_lock;
   Cond queue_cond;
   std::queue<Task*> task_queue;
-- 
2.39.5