buf_flush_page_cleaner_thread

while (srv_shutdown_state == SRV_SHUTDOWN_NONE) {    //1 server active或者有挂起的读IO请求或者n_flushed==0    //  sleep 1微妙    if (srv_check_activity(last_activity)    || buf_get_n_pending_read_ios()    || n_flushed == 0) {page_cleaner_sleep_if_needed(next_loop_time);    }    //2    next_loop_time = ut_time_ms() + 1000;    if (srv_check_activity(last_activity)) {        last_activity = srv_get_activity_count();        //2.1        n_flushed = buf_flush_LRU_tail();        //2.2        n_flushed += page_cleaner_flush_pages_if_needed();    }else{        n_flushed = page_cleaner_do_flush_batch(PCT_IO(100),LSN_MAX);        //刷srv_io_capacity个即200个page        //page_cleaner_do_flush_batch->buf_flush_list->buf_flush_batch->        //buf_do_flush_list_batch: 刷flush_list脏页    }}

注：

PCT_IO(100) ：200

#define PCT_IO(p) ((ulong) (srv_io_capacity * ((double) (p) / 100.0)))

大概是每秒调用一次：

2.1:buf_flush_LRU_tail

buf_flush_LRU//每次刷100个，扫描深度srv_LRU_scan_depth

     buf_flush_batch->count = buf_do_LRU_batch(buf_pool, 100);->

     buf_free_from_unzip_LRU_list_batch

     buf_flush_LRU_list_batch

   扫描深度是srv_LRU_scan_depth，每次检查100个block。优先检查unzip_LRU链表，然后LRU链表；如果有干净的页，则将其move到free链表。

问题：如果是热点页，岂不是就把热数据替换出去了？

2.2：page_cleaner_flush_pages_if_needed刷脏页，自动调整个数

主要涉及2个函数：

cur_lsn = log_get_lsn();oldest_lsn = buf_pool_get_oldest_modification();age = cur_lsn > oldest_lsn ? cur_lsn - oldest_lsn : 0;pct_for_dirty = af_get_pct_for_dirty();pct_for_lsn = af_get_pct_for_lsn(age);pct_total = ut_max(pct_for_dirty, pct_for_lsn);//avg_page_rate等于上一个srv_flushing_avg_loops循环里刷磁盘的脏页数的平均值//最大不会超过srv_max_io_capacity值n_pages = (PCT_IO(pct_total) + avg_page_rate) / 2;if (n_pages > srv_max_io_capacity) {    n_pages = srv_max_io_capacity;}n_pages = page_cleaner_do_flush_batch(n_pages, oldest_lsn + lsn_avg_rate * (age_factor + 1));