bthread set concurrency by tag

docs/cn/bthread_tagged_task_group.md

@@ -22,18 +22,23 @@ FLAGS_bthread_concurrency为所有分组的线程数的上限，FLAGS_bthread_mi
 一般情况应用创建的bthread不需要设置bthread_attr_t的tag字段，创建的bthread会在当前tag上下文中执行；如果希望创建的bthread不在当前tag上下文中执行，可以设置bthread_attr_t的tag字段为希望的值，这么做会对性能有些损失，关键路径上应该避免这么做。
 
 Q：如何动态改变分组线程的数量？
-A：当前每个分组的线程数最少为4个，所以先设置FLAGS_bthread_concurrency=4*分组数，再设置FLAGS_bthread_min_concurrency=FLAGS_bthread_concurrency，之后再把FLAGS_bthread_concurrency改大一些，之后再设置FLAGS_bthread_current_tag和FLAGS_bthread_concurrency_by_tag来改变某个分组的线程数。
+
+A：server的线程数最少为4个，后台任务线程数最少为2个，所以上面的例子中，FLAGS_bthread_concurrency最小值为4+4+2=10，再设置FLAGS_bthread_min_concurrency=FLAGS_bthread_concurrency，之后再把FLAGS_bthread_concurrency改大一些，之后再设置FLAGS_bthread_current_tag和FLAGS_bthread_concurrency_by_tag来改变某个分组的线程数。对于server，如果设置了ServerOption.bthread_tag，num_threads的含义是这个分组的线程数；如果没有设置（相当于没有启用分组，默认值为BTHREAD_TAG_INVALID）,num_thread的含义是所有分组的线程数。
 
 Q：不同分组之间有什么关系吗？
+
 A：不同分组是独立的线程池和事件驱动器，完全没有关系。
 
 Q：可以在分组之间做bthread的同步操作吗？
+
 A：可以的，每个bthread都有自己的tag标签，挂起后重新投入运行将继续在这个tag的线程池上执行。
 
 Q：客户端发送和接收RPC消息是在哪个分组上执行的？
+
 A：这取决于客户端的上下文，如果客户端不在任何tag分组上，那将使用tag0分组收发消息；否则将在当前所在的tag分组收发消息。
 
 Q：如何将一个分组的线程绑定到指定的一些cpu上面。
+
 A：int bthread_set_tagged_worker_startfn(void (*start_fn)(bthread_tag_t))这个函数用于在某个分组上做一些初始化的工作，比如：可以实现绑核的代码，根据tag入参来确定不同分组绑定不同的cpu。
 
 # 监控

example/bthread_tag_echo_c++/server.cpp

@@ -17,10 +17,10 @@
 
 // A server to receive EchoRequest and send back EchoResponse.
 
-#include <gflags/gflags.h>
-#include <butil/logging.h>
 #include <brpc/server.h>
 #include <bthread/unstable.h>
+#include <butil/logging.h>
+#include <gflags/gflags.h>
 #include "echo.pb.h"
 
 DEFINE_bool(echo_attachment, true, "Echo attachment as well");
@@ -29,6 +29,8 @@ DEFINE_int32(port2, 8003, "TCP Port of this server");
 DEFINE_int32(tag1, 0, "Server1 tag");
 DEFINE_int32(tag2, 1, "Server2 tag");
 DEFINE_int32(tag3, 2, "Background task tag");
+DEFINE_int32(num_threads1, 4, "Thread number of server1");
+DEFINE_int32(num_threads2, 4, "Thread number of server2");
 DEFINE_int32(idle_timeout_s, -1,
              "Connection will be closed if there is no "
              "read/write operations during the last `idle_timeout_s'");
@@ -63,8 +65,11 @@ static void my_tagged_worker_start_fn(bthread_tag_t tag) {
 }
 
 static void* my_background_task(void*) {
-    LOG(INFO) << "run background task tag=" << bthread_self_tag();
-    bthread_usleep(1000000UL);
+    while (true) {
+        LOG(INFO) << "run background task tag=" << bthread_self_tag();
+        bthread_usleep(1000000UL);
+    }
+    return nullptr;
 }
 
 int main(int argc, char* argv[]) {
@@ -102,6 +107,7 @@ int main(int argc, char* argv[]) {
     options1.max_concurrency = FLAGS_max_concurrency;
     options1.internal_port = FLAGS_internal_port1;
     options1.bthread_tag = FLAGS_tag1;
+    options1.num_threads = FLAGS_num_threads1;
     if (server1.Start(FLAGS_port1, &options1) != 0) {
         LOG(ERROR) << "Fail to start EchoServer";
         return -1;
@@ -127,6 +133,7 @@ int main(int argc, char* argv[]) {
     options2.max_concurrency = FLAGS_max_concurrency;
     options2.internal_port = FLAGS_internal_port2;
     options2.bthread_tag = FLAGS_tag2;
+    options2.num_threads = FLAGS_num_threads2;
     if (server2.Start(FLAGS_port2, &options2) != 0) {
         LOG(ERROR) << "Fail to start EchoServer";
         return -1;

src/brpc/server.cpp

@@ -149,7 +149,7 @@ ServerOptions::ServerOptions()
     , health_reporter(NULL)
     , rtmp_service(NULL)
     , redis_service(NULL)
-    , bthread_tag(BTHREAD_TAG_DEFAULT) {
+    , bthread_tag(BTHREAD_TAG_INVALID) {
     if (s_ncore > 0) {
         num_threads = s_ncore + 1;
     }
@@ -833,6 +833,17 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
 #endif
     }
 
+    auto original_bthread_tag = _options.bthread_tag;
+    if (original_bthread_tag == BTHREAD_TAG_INVALID) {
+        _options.bthread_tag = BTHREAD_TAG_DEFAULT;
+    }
+    if (_options.bthread_tag < BTHREAD_TAG_DEFAULT ||
+        _options.bthread_tag >= FLAGS_task_group_ntags) {
+        LOG(ERROR) << "Fail to set tag " << _options.bthread_tag << ", tag range is ["
+                   << BTHREAD_TAG_DEFAULT << ":" << FLAGS_task_group_ntags << ")";
+        return -1;
+    }
+
     if (_options.http_master_service) {
         // Check requirements for http_master_service:
         //  has "default_method" & request/response have no fields
@@ -1020,7 +1031,11 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
         if (_options.num_threads < BTHREAD_MIN_CONCURRENCY) {
             _options.num_threads = BTHREAD_MIN_CONCURRENCY;
         }
-        bthread_setconcurrency(_options.num_threads);
+        if (original_bthread_tag == BTHREAD_TAG_INVALID) {
+            bthread_setconcurrency(_options.num_threads);
+        } else {
+            bthread_setconcurrency_by_tag(_options.num_threads, _options.bthread_tag);
+        }
     }
 
     for (MethodMap::iterator it = _method_map.begin();
@@ -1085,12 +1100,6 @@ int Server::StartInternal(const butil::EndPoint& endpoint,
                 return -1;
             }
             _am->_use_rdma = _options.use_rdma;
-            if (_options.bthread_tag < BTHREAD_TAG_DEFAULT ||
-                _options.bthread_tag >= FLAGS_task_group_ntags) {
-                LOG(ERROR) << "Fail to set tag " << _options.bthread_tag << ", tag range is ["
-                           << BTHREAD_TAG_DEFAULT << ":" << FLAGS_task_group_ntags << ")";
-                return -1;
-            }
             _am->_bthread_tag = _options.bthread_tag;
         }
         // Set `_status' to RUNNING before accepting connections

src/bthread/bthread.cpp

@@ -392,18 +392,14 @@ int bthread_setconcurrency_by_tag(int num, bthread_tag_t tag) {
     if (tag < BTHREAD_TAG_DEFAULT || tag >= FLAGS_task_group_ntags) {
         return EPERM;
     }
+    auto c = bthread::get_or_new_task_control();
     BAIDU_SCOPED_LOCK(bthread::g_task_control_mutex);
-    auto c = bthread::get_task_control();
-    if (c == NULL) {
-        bthread::FLAGS_bthread_concurrency_by_tag = 0;
-        return 0;
-    }
     auto ngroup = c->concurrency();
     auto tag_ngroup = c->concurrency(tag);
     auto add = num - tag_ngroup;
     if (ngroup + add > bthread::FLAGS_bthread_concurrency) {
         LOG(ERROR) << "Fail to set concurrency by tag " << tag
-                   << ", Whole concurrency larger than bthread_concurrency";
+                   << ", Total concurrency larger than bthread_concurrency";
         return EPERM;
     }
     auto added = 0;