Add C bindings for LowerThreadPoolIO/CPUPriority (#5285)

Summary:
There were no C bindings for lowering thread pool priority. This adds those.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5285

Differential Revision: D15290050

Pulled By: siying

fbshipit-source-id: b2ed94d0c39d27434ace2204829a242b53d0d67a

db/c.cc

@@ -3268,6 +3268,22 @@ void rocksdb_env_join_all_threads(rocksdb_env_t* env) {
   env->rep->WaitForJoin();
 }
 
+void rocksdb_env_lower_thread_pool_io_priority(rocksdb_env_t* env) {
+  env->rep->LowerThreadPoolIOPriority();
+}
+
+void rocksdb_env_lower_high_priority_thread_pool_io_priority(rocksdb_env_t* env) {
+  env->rep->LowerThreadPoolIOPriority(Env::HIGH);
+}
+
+void rocksdb_env_lower_thread_pool_cpu_priority(rocksdb_env_t* env) {
+  env->rep->LowerThreadPoolCPUPriority();
+}
+
+void rocksdb_env_lower_high_priority_thread_pool_cpu_priority(rocksdb_env_t* env) {
+  env->rep->LowerThreadPoolCPUPriority(Env::HIGH);
+}
+
 void rocksdb_env_destroy(rocksdb_env_t* env) {
   if (!env->is_default) delete env->rep;
   delete env;

include/rocksdb/c.h

@@ -1301,6 +1301,11 @@ extern ROCKSDB_LIBRARY_API void
 rocksdb_env_set_high_priority_background_threads(rocksdb_env_t* env, int n);
 extern ROCKSDB_LIBRARY_API void rocksdb_env_join_all_threads(
     rocksdb_env_t* env);
+extern ROCKSDB_LIBRARY_API void rocksdb_env_lower_thread_pool_io_priority(rocksdb_env_t* env);
+extern ROCKSDB_LIBRARY_API void rocksdb_env_lower_high_priority_thread_pool_io_priority(rocksdb_env_t* env);
+extern ROCKSDB_LIBRARY_API void rocksdb_env_lower_thread_pool_cpu_priority(rocksdb_env_t* env);
+extern ROCKSDB_LIBRARY_API void rocksdb_env_lower_high_priority_thread_pool_cpu_priority(rocksdb_env_t* env);
+
 extern ROCKSDB_LIBRARY_API void rocksdb_env_destroy(rocksdb_env_t*);
 
 extern ROCKSDB_LIBRARY_API rocksdb_envoptions_t* rocksdb_envoptions_create();