Mysql必读从MySQL的源码剖析Innodb buffer的命中率计算
《Mysql必读从MySQL的源码剖析Innodb buffer的命中率计算》要点: 按官方手册推荐Innodb buffer Hit Ratios的计算是: 100-((iReads / iReadRequests)*100) iReads : mysql->status->Innodb_buffer_pool_reads iReadRequests: mysql->status->Innodb_buffer_pool_read_requests 出处: http://dev.mysql.com/doc/mysql-monitor/2.0/en/mem_graphref.html ? $ib_bp_read_ratio = sprintf "%.2f",($stats{'Innodb_buffer_pool_read_requests'} ? 100 - ($stats{'Innodb_buffer_pool_reads'} / $stats{'Innodb_buffer_pool_read_requests'}) * 100 :0); 即:? ib_bp_hit=100-(Innodb_buffer_pool_reads/Innodb_buffer_pool_read_requests)*100 另外我们知道查看Innodb Buffer Hit Ratios的地方是: Buffer pool hit rate : XXXX/1000; 那个XXX/1000即是buffer pool hit ratios的命中. 这样也可以从代码里看一下这个bp命中计算: storage/innobase/buf/buf0buf.c # void buf_print_io storage/innodbase/include/buf0buf.h #struct buf_block_struct 在buf0buf.c 中的buf_print_io函数中可以看到: void buf_print_io( … if (buf_pool->n_page_gets > buf_pool->n_page_gets_old) { fprintf(file,"Buffer pool hit rate %lu / 1000n",(ulong) (1000 - ((1000 * (buf_pool->n_pages_read - buf_pool->n_pages_read_old)) / (buf_pool->n_page_gets - buf_pool->n_page_gets_old)))); } else { fputs("No buffer pool page gets since the last printoutn",file); } buf_pool->n_page_gets_old = buf_pool->n_page_gets; buf_pool->n_pages_read_old = buf_pool->n_pages_read; … } 结合: struct buf_block_struct{ … ulint n_pages_read; /* number read operations */ … ulint n_page_gets; /* number of page gets performed; also successful searches through the adaptive hash index are counted as page gets; this field is NOT protected by the buffer pool mutex */ … ulint n_page_gets_old;/* n_page_gets when buf_print was last time called: used to calculate hit rate */ … ulint n_pages_read_old;/* n_pages_read when buf_print was last time called */ … ?MYSQL必读
ib_bp_hit=1000 C (t2.iReads C t1.iReads)/(t2.iReadRequest C t1.iReadRequest)*1000 t(n): 时间点 两个时间间隔最少是30秒以上,在小意义不大. iReads: Innodb_buffer_pool_reads iReadRequest: Innodb_buffer_pool_read_requests 对innodb的输出参数有兴趣的可以关注: storage/innobase/buf/Srv0srv.c 中的: void srv_export_innodb_status() 思考: 能解决的问题: (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |