aggregated_stats.h

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#ifndef AGGREGATED_STATS_H
#define AGGREGATED_STATS_H
 
#include "aggregated_stats_buffer.h"
#include "include/my_thread_local.h"  // my_thread_id
 
/**
   To facilitate calculating values of status variables aggregated per all THDs
   in real-time, each THD will update its stats into a matching buffer shard.
   Later we will aggregate the values accross all the shards to get the final
   values.
 
   This mechanism avoids possible contentions if all THDs would write directly
   to a single shared global buffer.
*/
struct aggregated_stats {
  constexpr static size_t STAT_SHARD_COUNT = 64;
 
  inline aggregated_stats_buffer &get_shard(my_thread_id thread_id) {
    const size_t shard_idx = thread_id % STAT_SHARD_COUNT;
    return shards_[shard_idx];
  }
  void flush();
  void get_total(aggregated_stats_buffer &result);
  uint64_t get_single_total(size_t offset);
 
 protected:
  aggregated_stats_buffer shards_[STAT_SHARD_COUNT];
};
 
#endif /* AGGREGATES_STATS_H */