[improve](scan) support lower the thread priority of scan thread (#24526)

The configuration item is used to lower the priority of the scanner thread,
typically employed to ensure CPU scheduling for write operations.

be/src/common/config.cpp

@@ -1088,6 +1088,8 @@ DEFINE_Int16(bitmap_serialize_version, "1");
 // the count of thread to group commit insert
 DEFINE_Int32(group_commit_insert_threads, "10");
 
+DEFINE_mInt32(scan_thread_nice_value, "0");
+
 #ifdef BE_TEST
 // test s3
 DEFINE_String(test_s3_resource, "resource");

be/src/common/config.h

@@ -1159,6 +1159,12 @@ DECLARE_Int16(bitmap_serialize_version);
 // This config can be set to limit thread number in group commit insert thread pool.
 DECLARE_mInt32(group_commit_insert_threads);
 
+// The configuration item is used to lower the priority of the scanner thread,
+// typically employed to ensure CPU scheduling for write operations.
+// Default is 0, which is default value of thread nice value, increase this value
+// to lower the priority of scan threads
+DECLARE_Int32(scan_thread_nice_value);
+
 #ifdef BE_TEST
 // test s3
 DECLARE_String(test_s3_resource);

be/src/util/thread.cpp

@@ -20,6 +20,8 @@
 
 #include "thread.h"
 
+#include <sys/resource.h>
+
 #ifndef __APPLE__
 // IWYU pragma: no_include <bits/types/struct_sched_param.h>
 #include <sched.h>
@@ -49,6 +51,7 @@
 #include <string>
 #include <vector>
 
+#include "common/config.h"
 #include "common/logging.h"
 #include "gutil/atomicops.h"
 #include "gutil/dynamic_annotations.h"
@@ -93,6 +96,8 @@ public:
 
 #ifndef __APPLE__
     static void set_idle_sched(int64_t tid);
+
+    static void set_thread_nice_value(int64_t tid);
 #endif
 
     // not the system TID, since pthread_t is less prone to being recycled.
@@ -174,6 +179,26 @@ void ThreadMgr::set_idle_sched(int64_t tid) {
         LOG(ERROR) << "set_thread_idle_sched";
     }
 }
+
+void ThreadMgr::set_thread_nice_value(int64_t tid) {
+    if (tid == getpid()) {
+        return;
+    }
+    // From Linux kernel:
+    // In the current implementation, each unit of difference in the nice values of two
+    // processes results in a factor of 1.25 in the degree to which the
+    // scheduler favors the higher priority process.  This causes very
+    // low nice values (+19) to truly provide little CPU to a process
+    // whenever there is any other higher priority load on the system,
+    // and makes high nice values (-20) deliver most of the CPU to
+    // applications that require it (e.g., some audio applications).
+
+    // Choose 5 as lower priority value, default is 0
+    int err = setpriority(PRIO_PROCESS, 0, config::scan_thread_nice_value);
+    if (err < 0 && errno != EPERM) {
+        LOG(ERROR) << "set_thread_low_priority";
+    }
+}
 #endif
 
 void ThreadMgr::add_thread(const pthread_t& pthread_id, const std::string& name,
@@ -305,6 +330,10 @@ void Thread::set_self_name(const std::string& name) {
 void Thread::set_idle_sched() {
     ThreadMgr::set_idle_sched(current_thread_id());
 }
+
+void Thread::set_thread_nice_value() {
+    ThreadMgr::set_thread_nice_value(current_thread_id());
+}
 #endif
 
 void Thread::join() {

be/src/util/thread.h

@@ -93,6 +93,8 @@ public:
 
 #ifndef __APPLE__
     static void set_idle_sched();
+
+    static void set_thread_nice_value();
 #endif
 
     ~Thread();

be/src/vec/exec/scan/scanner_scheduler.cpp

@@ -318,6 +318,14 @@ void ScannerScheduler::_scanner_scan(ScannerScheduler* scheduler, ScannerContext
         Thread::set_self_name("_scanner_scan");
     }
 #endif
+
+#ifndef __APPLE__
+    // The configuration item is used to lower the priority of the scanner thread,
+    // typically employed to ensure CPU scheduling for write operations.
+    if (config::scan_thread_nice_value != 0 && scanner->get_name() != VFileScanner::NAME) {
+        Thread::set_thread_nice_value();
+    }
+#endif
     scanner->update_wait_worker_timer();
     scanner->start_scan_cpu_timer();
     Status status = Status::OK();