什么可能导致 RDS 上的 MySQL 每 5 分钟出现一次 CPU 峰值？

Question

在相对写入密集的恒定负载下，我们在 RDS 上使用 MySQL 每 5 分钟就会遇到 CPU 峰值。有没有人经历过类似的事情或者知道可能是什么原因造成的？

MySQL版本：5.6.22 存储引擎：InnoDB

我们在使用磁盘和 SSD 磁盘的 M3 中型和 M3 大型实例类型上都遇到了峰值，无论我们是否启用了多可用区，它们都会发生。

我们的写入次数越多，峰值就越陡峭。然而，写入次数似乎并不影响频率。我们写完后，他们会继续一段时间。它们不会出现在只读负载下。

以下是 InnoDB 变量：

innodb_adaptive_flushing: ON
innodb_adaptive_flushing_lwm: 10
innodb_adaptive_hash_index: ON
innodb_adaptive_max_sleep_delay: 150000
innodb_additional_mem_pool_size: 8388608
innodb_api_bk_commit_interval: 5
innodb_api_disable_rowlock: OFF
innodb_api_enable_binlog: OFF
innodb_api_enable_mdl: OFF
innodb_api_trx_level: 0
innodb_autoextend_increment: 64
innodb_autoinc_lock_mode: 1
innodb_buffer_pool_dump_at_shutdown: OFF
innodb_buffer_pool_dump_now: OFF
innodb_buffer_pool_filename: ib_buffer_pool
innodb_buffer_pool_instances: 8
innodb_buffer_pool_load_abort: OFF
innodb_buffer_pool_load_at_startup: OFF
innodb_buffer_pool_load_now: OFF
innodb_buffer_pool_size: 5705302016
innodb_change_buffer_max_size: 25
innodb_change_buffering: all
innodb_checksum_algorithm: innodb
innodb_checksums: ON
innodb_cmp_per_index_enabled: OFF
innodb_commit_concurrency: 0
innodb_compression_failure_threshold_pct: 5
innodb_compression_level: 6
innodb_compression_pad_pct_max: 50
innodb_concurrency_tickets: 5000
innodb_data_file_path: ibdata1:12M:autoextend
innodb_data_home_dir: /rdsdbdata/db/innodb
innodb_disable_sort_file_cache: OFF
innodb_doublewrite: ON
innodb_fast_shutdown: 1
innodb_file_format: Antelope
innodb_file_format_check: ON
innodb_file_format_max: Antelope
innodb_file_per_table: ON
innodb_flush_log_at_timeout: 1
innodb_flush_log_at_trx_commit: 1
innodb_flush_method: O_DIRECT
innodb_flush_neighbors: 1
innodb_flushing_avg_loops: 30
innodb_force_load_corrupted: OFF
innodb_force_recovery: 0
innodb_ft_aux_table: 
innodb_ft_cache_size: 8000000
innodb_ft_enable_diag_print: OFF
innodb_ft_enable_stopword: ON
innodb_ft_max_token_size: 84
innodb_ft_min_token_size: 3
innodb_ft_num_word_optimize: 2000
innodb_ft_result_cache_limit: 2000000000
innodb_ft_server_stopword_table: 
innodb_ft_sort_pll_degree: 2
innodb_ft_total_cache_size: 640000000
innodb_ft_user_stopword_table: 
innodb_io_capacity: 200
innodb_io_capacity_max: 2000
innodb_large_prefix: OFF
innodb_lock_wait_timeout: 50
innodb_locks_unsafe_for_binlog: OFF
innodb_log_buffer_size: 8388608
innodb_log_compressed_pages: ON
innodb_log_file_size: 134217728
innodb_log_files_in_group: 2
innodb_log_group_home_dir: /rdsdbdata/log/innodb
innodb_lru_scan_depth: 1024
innodb_max_dirty_pages_pct: 75
innodb_max_dirty_pages_pct_lwm: 0
innodb_max_purge_lag: 0
innodb_max_purge_lag_delay: 0
innodb_mirrored_log_groups: 1
innodb_monitor_disable: 
innodb_monitor_enable: 
innodb_monitor_reset: 
innodb_monitor_reset_all: 
innodb_old_blocks_pct: 37
innodb_old_blocks_time: 1000
innodb_online_alter_log_max_size: 134217728
innodb_open_files: 2000
innodb_optimize_fulltext_only: OFF
innodb_page_size: 16384
innodb_print_all_deadlocks: OFF
innodb_purge_batch_size: 300
innodb_purge_threads: 1
innodb_random_read_ahead: OFF
innodb_read_ahead_threshold: 56
innodb_read_io_threads: 4
innodb_read_only: OFF
innodb_replication_delay: 0
innodb_rollback_on_timeout: OFF
innodb_rollback_segments: 128
innodb_sort_buffer_size: 1048576
innodb_spin_wait_delay: 6
innodb_stats_auto_recalc: ON
innodb_stats_method: nulls_equal
innodb_stats_on_metadata: OFF
innodb_stats_persistent: ON
innodb_stats_persistent_sample_pages: 20
innodb_stats_sample_pages: 8
innodb_stats_transient_sample_pages: 8
innodb_status_output: OFF
innodb_status_output_locks: OFF
innodb_strict_mode: OFF
innodb_support_xa: ON
innodb_sync_array_size: 1
innodb_sync_spin_loops: 30
innodb_table_locks: ON
innodb_thread_concurrency: 0
innodb_thread_sleep_delay: 10000
innodb_undo_directory: .
innodb_undo_logs: 128
innodb_undo_tablespaces: 0
innodb_use_native_aio: ON
innodb_use_sys_malloc: ON
innodb_version: 5.6.22
innodb_write_io_threads: 4

谢谢！

Answer 1

我假设您提供的

VARIABLES

是用于

m3.large

？

对于 SSD，我很确定

innodb_flush_neighbors

应该为 0。（令我惊讶的是亚马逊没有注意到这一点。） http://dev.mysql.com/doc/refman/5.6/en/optimizing-innodb-diskio.html

尝试将

innodb_flushing_avg_loops

增加到 200。“增加该值可以使刷新操作的速率随着工作负载的变化而平稳、逐渐地变化。”

innodb_read_io_threads

和

innodb_write_io_threads

8 可能会更好。

“adaptive_flushing”听起来很相关，但我对此了解不够，无法发表评论。

如果这些还不够，请

• 再解释一下处理过程，
• 说明是否有任何 cron 作业正在运行

  */5

  ,
• 任何在 MySQL 中声明并处于活动状态的

  EVENTs

• 以及任何其他线索。

此外，您还可以提供这些信息以便更深入地研究设置。 （我没有要求它们，因为我没有任何关于在哪里寻找尖峰的好线索。）

• 显示变量；
• 显示全球状态； -- 假设它已经上涨至少一天了。