列表头部：最近访问过的新（“年轻”）页子列表At the head, a sublist of new (“young”) pages that were accessed recently

列表尾部：较少最近访问的旧页子列表At the tail, a sublist of old pages that were accessed less recently

缓冲池的 3/8 用于旧子列表。3/8 of the buffer pool is devoted to the old sublist.

列表的中点是新子列表尾部与旧子列表头部的边界。The midpoint of the list is the boundary where the tail of the new sublist meets the head of the old sublist.

当InnoDB将页面读入缓冲池时，最初会将其插入到中点位置（旧子列表的头部）。页面可能被读取，是由于用户发起的操作（如 SQL 查询）所需，或作为InnoDB自动执行的预读操作的一部分。When InnoDB reads a page into the buffer pool, it initially inserts it at the midpoint (the head of the old sublist). A page can be read because it is required for a user-initiated operation such as an SQL query, or as part of a read-ahead operation performed automatically by InnoDB.

访问旧子列表中的页面会使其“年轻”，并将其移到新子列表的头部。如果该页面是由于用户发起的操作而被读取，第一次访问会立即发生，并且页面会被标记为年轻。如果该页面是由于预读操作而被读取，第一次访问不会立即发生，并且在页面被驱逐之前可能根本不会发生。Accessing a page in the old sublist makes it “young”, moving it to the head of the new sublist. If the page was read because it was required by a user-initiated operation, the first access occurs immediately and the page is made young. If the page was read due to a read-ahead operation, the first access does not occur immediately and might not occur at all before the page is evicted.

As the database operates, pages in the buffer pool that are not accessed “年龄” by moving toward the tail of the list. Pages in both the new and old sublists age as other pages are made new. Pages in the old sublist also age as pages are inserted at the midpoint. Eventually, a page that remains unused reaches the tail of the old sublist and is evicted.As the database operates, pages in the buffer pool that are not accessed “age” by moving toward the tail of the list. Pages in both the new and old sublists age as other pages are made new. Pages in the old sublist also age as pages are inserted at the midpoint. Eventually, a page that remains unused reaches the tail of the old sublist and is evicted.

理想情况下，您应将缓冲池的大小设置为尽可能大的值，同时留出足够的内存供服务器上的其他进程运行，以避免过度分页。缓冲池越大，InnoDB 就越像一个内存数据库，一旦从磁盘读取数据，后续读取就会从内存中访问数据。参见 第 17.8.3.1 节，“配置 InnoDB 缓冲池大小”。Ideally, you set the size of the buffer pool to as large a value as practical, leaving enough memory for other processes on the server to run without excessive paging. The larger the buffer pool, the more InnoDB acts like an in-memory database, reading data from disk once and then accessing the data from memory during subsequent reads. See Section 17.8.3.1, “Configuring InnoDB Buffer Pool Size”.

在具有足够内存的 64 位系统上，您可以将缓冲池拆分为多个部分，以最小化并发操作中对内存结构的争用。详情请参见 第 17.8.3.2 节，“配置多个缓冲池实例”。On 64-bit systems with sufficient memory, you can split the buffer pool into multiple parts to minimize contention for memory structures among concurrent operations. For details, see Section 17.8.3.2, “Configuring Multiple Buffer Pool Instances”.

无论操作是否会将大量不常访问的数据带入缓冲池，您都可以将经常访问的数据保存在内存中。详情请参阅 第 17.8.3.3 节，“使缓冲池抗扫描”。You can keep frequently accessed data in memory regardless of sudden spikes of activity from operations that would bring large amounts of infrequently accessed data into the buffer pool. For details, see Section 17.8.3.3, “Making the Buffer Pool Scan Resistant”.

您可以控制如何以及何时执行预读请求，以异步预取页面到缓冲池中，以应对即将到来的访问需求。详情请参阅 第 17.8.3.4 节，“配置 InnoDB 缓冲池预取（预读）”。You can control how and when to perform read-ahead requests to prefetch pages into the buffer pool asynchronously in anticipation of impending need for them. For details, see Section 17.8.3.4, “Configuring InnoDB Buffer Pool Prefetching (Read-Ahead)”.

您可以控制后台刷新发生的时间，以及刷新速率是否根据工作负载动态调整。有关详细信息，请参阅 第 17.8.3.5 节，“配置缓冲池刷新”。You can control when background flushing occurs and whether or not the rate of flushing is dynamically adjusted based on workload. For details, see Section 17.8.3.5, “Configuring Buffer Pool Flushing”.

您可以配置 InnoDB 如何保留当前缓冲池状态，以避免在服务器重启后经历长时间的预热期。有关详细信息，请参阅 第 17.8.3.6 节，“保存和恢复缓冲池状态”。You can configure how InnoDB preserves the current buffer pool state to avoid a lengthy warmup period after a server restart. For details, see Section 17.8.3.6, “Saving and Restoring the Buffer Pool State”.

youngs/s 指标仅适用于旧页面。它基于页面访问次数。对于给定页面可以有多次访问，所有访问都会被计数。如果在没有大量扫描的情况下看到非常低的 youngs/s 值，请考虑减少延迟时间或增加用于旧子列表的缓冲池百分比。增加百分比会使旧子列表变大，从而使该子列表中的页面移动到尾部所需的时间更长，这会增加这些页面再次被访问并变年轻的可能性。参见 第 17.8.3.3 节，“使缓冲池具备扫描抵抗能力”。The youngs/s metric is applicable only to old pages. It is based on the number of page accesses. There can be multiple accesses for a given page, all of which are counted. If you see very low youngs/s values when there are no large scans occurring, consider reducing the delay time or increasing the percentage of the buffer pool used for the old sublist. Increasing the percentage makes the old sublist larger so that it takes longer for pages in that sublist to move to the tail, which increases the likelihood that those pages are accessed again and made young. See Section 17.8.3.3, “Making the Buffer Pool Scan Resistant”.

non-youngs/s 指标仅适用于旧页。它基于页面访问次数。某个页面可能有多次访问，所有访问都会被计数。如果在执行大表扫描时没有看到更高的 non-youngs/s 值（以及更高的 youngs/s 值），请增加延迟值。请参见 第 17.8.3.3 节，“使缓冲池扫描具有抗性”。The non-youngs/s metric is applicable only to old pages. It is based on the number of page accesses. There can be multiple accesses for a given page, all of which are counted. If you do not see a higher non-youngs/s value when performing large table scans (and a higher youngs/s value), increase the delay value. See Section 17.8.3.3, “Making the Buffer Pool Scan Resistant”.

该young-making rate accounts for all buffer pool page accesses, not just accesses for pages in the old sublist. The young-making rate and not rate do not normally add up to the overall buffer pool hit rate. Page hits in the old sublist cause pages to move to the new sublist, but page hits in the new sublist cause pages to move to the head of the list only if they are a certain distance from the head.The young-making rate accounts for all buffer pool page accesses, not just accesses for pages in the old sublist. The young-making rate and not rate do not normally add up to the overall buffer pool hit rate. Page hits in the old sublist cause pages to move to the new sublist, but page hits in the new sublist cause pages to move to the head of the list only if they are a certain distance from the head.

not (young-making rate) 是平均命中率，当页访问未能使页面变年轻时，由于未满足 innodb_old_blocks_time 定义的延迟，或者由于新子列表中的页面命中未导致页面移动到头部。该比率计入所有缓冲池页面访问，而不仅仅是对旧子列表中页面的访问。not (young-making rate) is the average hit rate at which page accesses have not resulted in making pages young due to the delay defined by innodb_old_blocks_time not being met, or due to page hits in the new sublist that did not result in pages being moved to the head. This rate accounts for all buffer pool page accesses, not just accesses for pages in the old sublist.