如何确认第二个sskgslcas就是获得Buffer Pin锁

从dtrace日志中贴出部分日志:
   0  51768           kcbgtcr:entry i=643 PID::entry:==pid1555:oracle:kcbgtcr:entry fffffd7ffac27cd8 0 2fe 0 23dede0 fffffd7fffdfa790
   0  51769           sskgslcas:entry i=644 PID::entry:==pid1555:oracle:sskgslcas:entry 3a4282a90 0 1 0 0 3a4c8b1a0
   0  60716           ktrexf:entry i=645 PID::entry:==pid1555:oracle:ktrexf:entry fffffd7fffdfa790 d7fcd60 0 15398551572 1fe8 23dc9f0
   0  64186           kcbzgs:entry i=646 PID::entry:==pid1555:oracle:kcbzgs:entry 1 d7fcd60 0 0 395fe35c8 23dc9f0
   0  53941           kssadf_numa_intl:entry i=647 PID::entry:==pid1555:oracle:kssadf_numa_intl:entry 23 3a41458b0 3a4874d70 0 0 13
   0  51769           sskgslcas:entry i=648 PID::entry:==pid1555:oracle:sskgslcas:entry 395fe3610 0 1 0 395fe35c8 395fe35c8  -------如果判断这个就是buffer pin呢?????

   0 128723          sskgsldecr:entry i=649 PID::entry:==pid1555:oracle:sskgsldecr:entry 3a4282a90 1 1 0 1 2000000000000000

为了能更好的解释,我再次用dtrace跟踪 一把,先查一下本会话下的进程号:
 SQL> select spid from v$session s,v$process b where s.paddr=b.addr and s.sid in(select sid from v$mystat where rownum=1);
 SPID
 ------------------------
 1555
 进程号为1555
 
SQL>  select rowid,dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,id,name from gyj.t1¡¡where rownum=1;
 ROWID                   FILE#     BLOCK#         ID NAME
 ------------------ ---------- ---------- ---------- ----------------------------------------------------------------------------------------------------
 AAASP9AAGAAAACHAAA         6        135        1 gyj1
 
SQL> select hladdr from x$bh where file#=6 and dbablk=135;
 HLADDR
 ----------------
 00000003A4282A90
 
SQL> select id,name from gyj.t1 where rowid='AAASP9AAGAAAACHAAA';
         ID NAME
 ---------- ----------------------------------------------------------------------------------------------------
          1 gyj1
 
接着用dtrace跟踪这个进程:
 bash-3.2# ./dtrace.d -x switchrate=1hz -b 32m 1555 > dtrace111.log
 dtrace: script './dtrace.d' matched 160196 probes
 
然后会到回话号1555中执行
 SQL> select id,name from gyj.t1 where rowid='AAASP9AAGAAAACHAAA';
         ID NAME
 ---------- ----------------------------------------------------------------------------------------------------
          1 gyj1
 
从dtrace日志中贴出的部分日志:
   0  51768             kcbgtcr:entry i=643 PID::entry:==pid1555:oracle:kcbgtcr:entry fffffd7ffac27cd8 0 2fe 0 23dede0 fffffd7fffdfa790
   0  51769                  sskgslcas:entry i=644 PID::entry:==pid1555:oracle:sskgslcas:entry 3a4282a90 0 1 0 0 3a4c8b1a0
   0  60716                     ktrexf:entry i=645 PID::entry:==pid1555:oracle:ktrexf:entry fffffd7fffdfa790 d7fcd60 0 15398551572 1fe8 23dc9f0
   0  64186                     kcbzgs:entry i=646 PID::entry:==pid1555:oracle:kcbzgs:entry 1 d7fcd60 0 0 395fe35c8 23dc9f0
   0  53941           kssadf_numa_intl:entry i=647 PID::entry:==pid1555:oracle:kssadf_numa_intl:entry 23 3a41458b0 3a4874d70 0 0 13
   0  51769                  sskgslcas:entry i=648 PID::entry:==pid1555:oracle:sskgslcas:entry 395fe3610 0 1 0 395fe35c8 395fe35c8  -------如果判断这个就是buffer pin呢?????
   0 128723                 sskgsldecr:entry i=649 PID::entry:==pid1555:oracle:sskgsldecr:entry 3a4282a90 1 1 0 1 2000000000000000
 
dump出buffer header日志,找到6号文件135号块的bh
 SQL> alter session set events 'immediate trace name buffers level 1';
 直接dump6号文件135号块也可以,11g可以直接看块上的BH:
SQL> alter system dump datafile 6 block 135;

---红色部分就是6号文件135号块的bh的信息
 BH (0x395fe35c8) file#: 6 rdba: 0x01800087 (6/135) class: 1 ba: 0x395d34000 
  set: 5 pool 3 bsz: 8192 bsi: 0 sflg: 2 pwc: 245,28
   dbwrid: 0 obj: 74749 objn: 74749 tsn: 7 afn: 6 hint: f
   hash: [0x3a42842b0,0x3a42842b0] lru: [0x395fe37e0,0x395fe3580]
   ckptq: [NULL] fileq: [NULL] objq: [0x395fe3808,0x3947e6b18]
   st: XCURRENT md: NULL tch: 38
   flags: block_written_once redo_since_read
   LRBA: [0x0.0.0] LSCN: [0x0.0] HSCN: [0xffff.ffffffff] HSUB: [1]
   cr pin refcnt: 0 sh pin refcnt: 0




 0  51769         sskgslcas:entry i=648 PID::entry:==pid1555:oracle:sskgslcas:entry 395fe3610 0 1 0 395fe35c8 395fe35c8 
BH (0x395fe35c8)  ---这是6号文件135号块的BH地址


 比较0x395fe35c8和0x395fe3610的地址偏移量相差72个字节,一个BH大小约200字节,即buffer pin位于BH的第72个字节
 
用oradebug查一下buffer pin的值
 SQL> oradebug peek 0x395fe3610 4
 [395FE3610, 395FE3614) = 00000001   --获得buffer pin
 SQL> oradebug peek 0x395fe3610 4
 [395FE3610, 395FE3614) = 00000000  --释放buffer pin
 


可以配合mdb设断点来观察buffer pin的值
 -bash-3.2# mdb -p 1555
 Loading modules: [ ld.so.1 libc.so.1 ]
 > kcbgtcr:b  --开始逻辑读
 > :c
 mdb: stop at kcbgtcr
 mdb: target stopped at:
 kcbgtcr:        pushq  %rbp
 > sskgsldecr:b --获得Buffer Pin马上释放CBC Latch
 > :c
 mdb: stop at sskgsldecr
 mdb: target stopped at:
 sskgsldecr:     lock subq %rsi,(%rdi)
 > ::delete all
 > kcbrls:b   --释放Buffer Pin
 > :c
 mdb: stop at kcbrls
 mdb: target stopped at:
 kcbrls:         pushq  %rbp
 > sskgsldecr:b  --释放CBC Latch
 > :c
 mdb: stop at sskgsldecr
 mdb: target stopped at:
 sskgsldecr:     lock subq %rsi,(%rdi)
 > ::quit

 

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