From bfc82bd43317d8c4ab75433293f1dc012aeaf8b1 Mon Sep 17 00:00:00 2001
From: obdev <obdev@oceanbase.com>
Date: Fri, 24 Feb 2023 13:44:18 +0000
Subject: [PATCH] BUGFIX: break infinite loop of write throttle

---
 src/share/allocator/ob_fifo_arena.cpp  | 50 +++++++++++++++++++-------
 src/storage/ob_storage_table_guard.cpp |  3 +-
 src/storage/tablelock/ob_obj_lock.cpp  |  2 +-
 3 files changed, 41 insertions(+), 14 deletions(-)

diff --git a/src/share/allocator/ob_fifo_arena.cpp b/src/share/allocator/ob_fifo_arena.cpp
index 54cef08a0e..e1b6a4fbfe 100644
--- a/src/share/allocator/ob_fifo_arena.cpp
+++ b/src/share/allocator/ob_fifo_arena.cpp
@@ -10,6 +10,7 @@
  * See the Mulan PubL v2 for more details.
  */
 
+#define USING_LOG_PREFIX COMMON
 #include "ob_fifo_arena.h"
 #ifdef OB_USE_ASAN
 #include <malloc.h>
@@ -365,23 +366,48 @@ int64_t ObFifoArena::expected_wait_time(const int64_t seq) const
   return expected_wait_time;
 }
 
+// how much memory we can get after dt time.
 int64_t ObFifoArena::calc_mem_limit(const int64_t cur_mem_hold, const int64_t trigger_mem_limit, const int64_t dt) const
 {
-  double cur_chunk_seq = static_cast<double>(((cur_mem_hold - trigger_mem_limit) + MEM_SLICE_SIZE - 1)/ (MEM_SLICE_SIZE));
+  int ret = OB_SUCCESS;
   int64_t mem_can_be_assigned = 0;
 
-  int64_t allocate_size_in_the_page = MEM_SLICE_SIZE - (cur_mem_hold - trigger_mem_limit) % MEM_SLICE_SIZE;
-  int64_t accumulate_interval = 0;
-  int64_t the_page_interval = 0;
-  while (accumulate_interval < dt) {
-    the_page_interval = static_cast<int64_t>(throttle_info_.decay_factor_ * cur_chunk_seq * cur_chunk_seq * cur_chunk_seq) * allocate_size_in_the_page / MEM_SLICE_SIZE;
-    accumulate_interval += the_page_interval;
+  int64_t init_seq = ((cur_mem_hold - trigger_mem_limit) + MEM_SLICE_SIZE - 1) / (MEM_SLICE_SIZE);
+  int64_t init_page_left_size = MEM_SLICE_SIZE - (cur_mem_hold - trigger_mem_limit) % MEM_SLICE_SIZE;
+  double init_page_left_interval =  (1.0 * throttle_info_.decay_factor_ * pow(init_seq, 3) *
+                                     init_page_left_size / MEM_SLICE_SIZE);
+  double past_interval = throttle_info_.decay_factor_ * pow(init_seq, 2) * pow(init_seq + 1, 2) / 4;
+  double last_page_interval = 0;
+  double mid_result = 0;
+  double approx_max_chunk_seq = 0;
+  int64_t max_seq = 0;
+  double accumulate_interval = 0;
+  if (init_page_left_interval > dt) {
+    last_page_interval = throttle_info_.decay_factor_ * pow(init_seq, 3);
+    mem_can_be_assigned = dt / last_page_interval * MEM_SLICE_SIZE;
+  } else {
+    mid_result = 4.0 * (dt + past_interval - init_page_left_interval) / throttle_info_.decay_factor_;
+    approx_max_chunk_seq = pow(mid_result, 0.25);
+    max_seq = floor(approx_max_chunk_seq);
+    for (int i = 0; i < 2; i++) {
+      if (pow(max_seq, 2) * pow(max_seq + 1, 2) < mid_result) {
+        max_seq = max_seq + 1;
+      }
+    }
+    accumulate_interval = pow(max_seq, 2) * pow(max_seq + 1, 2) * throttle_info_.decay_factor_ / 4 - past_interval + init_page_left_interval;
+    mem_can_be_assigned = init_page_left_size + (max_seq - init_seq) * MEM_SLICE_SIZE;
+    if (accumulate_interval > dt) {
+      last_page_interval = throttle_info_.decay_factor_ * pow(max_seq, 3);
+      mem_can_be_assigned -= (accumulate_interval - dt) / last_page_interval * MEM_SLICE_SIZE;
+    }
+  }
 
-    mem_can_be_assigned += (accumulate_interval > dt ?
-                            allocate_size_in_the_page - (accumulate_interval - dt) * allocate_size_in_the_page / the_page_interval :
-                            allocate_size_in_the_page);
-    allocate_size_in_the_page = MEM_SLICE_SIZE;
-    cur_chunk_seq += double(1);
+  // defensive code
+  if (pow(max_seq, 2) * pow(max_seq + 1, 2) < mid_result) {
+    LOG_ERROR("unexpected result", K(max_seq), K(mid_result));
+  }
+  if (cur_mem_hold < trigger_mem_limit) {
+    LOG_ERROR("we should not limit speed now", K(cur_mem_hold), K(trigger_mem_limit));
   }
 
   return mem_can_be_assigned;
diff --git a/src/storage/ob_storage_table_guard.cpp b/src/storage/ob_storage_table_guard.cpp
index e6855a97d2..a6c9faa2cb 100644
--- a/src/storage/ob_storage_table_guard.cpp
+++ b/src/storage/ob_storage_table_guard.cpp
@@ -103,7 +103,8 @@ ObStorageTableGuard::~ObStorageTableGuard()
       }
     }
 
-    if (REACH_TIME_INTERVAL(100 * 1000L)) {
+    if (REACH_TIME_INTERVAL(100 * 1000L) &&
+        sleep_time > 0) {
       int64_t cost_time = ObTimeUtility::current_time() - init_ts_;
       LOG_INFO("throttle situation", K(sleep_time), K(time), K(seq), K(for_replay_), K(cost_time));
     }
diff --git a/src/storage/tablelock/ob_obj_lock.cpp b/src/storage/tablelock/ob_obj_lock.cpp
index bbacc0342b..3d94210419 100644
--- a/src/storage/tablelock/ob_obj_lock.cpp
+++ b/src/storage/tablelock/ob_obj_lock.cpp
@@ -462,7 +462,7 @@ int ObOBJLock::fast_lock(
                                lock_mode_in_same_trans,
                                need_retry,
                                conflict_tx_set))) {
-      if (OB_TRY_LOCK_ROW_CONFLICT != ret) {
+      if (OB_TRY_LOCK_ROW_CONFLICT != ret && OB_EAGAIN != ret) {
         LOG_WARN("try fast lock failed", KR(ret), K(lock_op));
       }
     } else {