按官方手冊(cè)推薦Innodb buffer Hit Ratios的計(jì)算是:
100-((iReads / iReadRequests)*100)iReads : mysql->status->Innodb_buffer_pool_readsiReadRequests: mysql->status->Innodb_buffer_pool_read_requests
出處: http://dev.mysql.com/doc/mysql-monitor/2.0/en/mem_graphref.html
搜”Hit Ratios”
推薦有興趣的同學(xué)把這個(gè)頁(yè)面都看一下應(yīng)該也會(huì)有很大收獲.
另外在hackmysql: www.hackmysql.com網(wǎng)站上的: mysqlsqlreport中關(guān)于buffer命中計(jì)算是:
$ib_bp_read_ratio = sprintf "%.2f",($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
另外我們知道查看Innodb Buffer Hit Ratios的地方是:
storage/innobase/buf/buf0buf.c # void buf_print_iostorage/innodbase/include/buf0buf.h #struct buf_block_struct
在buf0buf.c 中的buf_print_io函數(shù)中可以看到:
voidbuf_print_io(… if (buf_pool->n_page_gets > buf_pool->n_page_gets_old) {fprintf(file, "Buffer pool hit rate %lu / 1000/n",(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 printout/n",file);} buf_pool->n_page_gets_old = buf_pool->n_page_gets;buf_pool->n_pages_read_old = buf_pool->n_pages_read;…}結(jié)合:
storage/innobase/include/buf0buf.h中
struct buf_block_struct{…ulint n_pages_read; /* number read operations */…ulint n_page_gets; /* number of page gets performed;also successful searches throughthe adaptive hash index arecounted as page gets; this fieldis NOT protected by the bufferpool mutex */…ulint n_page_gets_old;/* n_page_gets when buf_print waslast time called: used to calculatehit rate */…ulint n_pages_read_old;/* n_pages_read when buf_print waslast time called */…
從這個(gè)來(lái)看innodb buffer hit Ratios的命中計(jì)算需要本次取的值和上次值做一個(gè)減法公式應(yīng)該為