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Experimental change to solve performance overshooting issue #1286

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Experimental change to solve performance overshooting issue #1286

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2 changes: 2 additions & 0 deletions plugin/clone/src/clone_client.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -228,6 +228,8 @@ uint64_t Client_Stat::task_target(uint64_t target_speed, uint64_t current_speed,
not set yet, start by assuming all active thread. */
auto active_tasks =
(current_target == 0) ? num_tasks : (current_speed / current_target);

active_tasks = num_tasks;
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The issue here is the calculation of active tasks is not correct. Let's say, the current_target is 700MB/S, and the current_speed is 900MB/S. Then the active_tasks will be 1.

According to the calculation for task_target below, the task target will be 700MB/s.
auto task_target = target_speed / active_tasks;
The task_target will be used as the current_target of next call of this task_target() function. Hence, it will go over the above calculation again and the task target speed will not be updated at all.

Since the max speed capacity for each thread is around 450MB/s, it will never throttle the thread. (Because it's always smaller than the target task speed 700MB/s).

For the change I made, I assume all threads created are active.

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Why InnoDB clone does not exhibit the issue?


/* Keep the value within current boundary. */
if (active_tasks == 0) {
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