简介：我有一个带ssd和512mb ram（1024mb突发）的Debian8VPS，只与mysql一起使用。我已经关闭了所有不必要的服务，并提供了数据库和系统上的所有资源。我只有5个工作站。ping和网络稳定。
主要问题是，如果我连续进行10次这样的查询：

(SELECT IFNULL(SUM(Qtty), 0) FROM operations
WHERE blablabla
FROM (goods LEFT JOIN store ON goods.ID = store.GdID)
WHERE Deleted <> -1
GROUP BY goods.ID;

随机5-6个执行2秒，其余执行8秒以上！我看没有理由这样做。当我激活slow\u query\u log时，它只有相同的查询，没有其他内容。
我的innodb数据是98mb，有没有理由给innodb提供更多的ram\u缓冲区\u池\u大小或者128就足够了？
innodb日志文件大小必须为25%-50%，哪个大小对我更合适？
tmp dir是tmpfs，所以如果tmp\u table\u size放在那里，有没有理由给它更多的ram或者足够使用1m呢？
table\u open\u cache-我有大约200个表，是否有任何理由按照mysqltuner的建议将其设置为20000个？
我能换点别的吗？

我的.cnf

skip-external-locking
skip-name-resolve
performance_schema = OFF
thread_stack = 192K
thread_cache_size = 10 #this is managed globally and is equal to max_connections
max_connections = 10
max_connect_errors = 10
connect_timeout = 20
wait_timeout = 20
interactive_timeout = 20
sql_mode = TRADITIONAL
default_storage_engine = InnoDB
innodb_buffer_pool_instances = 1
innodb_buffer_pool_size = 250M
innodb_log_file_size = 100M
innodb_strict_mode = ON
innodb_flush_method = O_DIRECT
innodb_flush_neighbors = 0
innodb_read_io_threads = 4
innodb_write_io_threads = 4
innodb_io_capacity = 2000
innodb_io_capacity_max = 3000
key_buffer = 128K
delay_key_write = ON
tmp_table_size = 10M # 32M = 53% temp
max_heap_table_size = 10M
query_cache_type = 0
query_cache_size = 0
table_open_cache = 5000
table_definition_cache = 3000