Swap Consumed very Much When PostgreSQL autovacuum to prevent wraparound

今天接到监控组的告警，某数据库服务器的SWAP分区消耗超过阀值，消耗约8G。 free total used free shared buffers cached Mem: 24682828 24607764 75064 0 10128 6525184 -/+ buffers/cache: 18072452 6610376 Swap: 16779884 8794580 7985304 查看过往的SAR报告如下 kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad 02-06 Average: 79193 24603635 99.68 27148 8510109 13953197 2826687 16.85 967 02-07 Average: 81699 24601129 99.67 23619 8483106 13953178 2826706 16.85 985 02-08 Average: 73905 24608923 99.70 11064 8504025 13953172 2826712 16.85 970 02-09 Average: 78953 24603875 99.68 18140 8475291 13953172 2826712 16.85 968 02-10 09:20:01 AM 74356 24608472 99.70 2580 8361932 13953172 2826712 16.85 968 09:30:01 AM 74224 24608604 99.70 3412 8466448 13822936 2956948 17.62 2956 Average: 77257 24605571 99.69 7574 8344604 13196771 3583113 21.35 1432 02-11 Average: 87933 24594895 99.64 10818 7304608 10841381 5938503 35.39 2315 02-12 Average: 82804 24600024 99.66 15113 7149277 10581682 6198202 36.94 1978 02-13 Average: 85698 24597130 99.65 7834 7246716 10130720 6649164 39.63 3248 TODAY Average: 73259 24609569 99.70 4444 6649324 8273769 8506115 50.69 21545 数据库日志中包含大量autovacuum 信息,其中有的执行时间比较长。（正常情况下一个autovacuum进程可以占用做多maintenance_work_mem设置的内存大小） # 查看服务器上占用内存较多的进程pmem (百分比) ps -eo user,RSSize,vsize,sz,size,pmem,cmd --sort size|grep postgres 以下进程占用70%物理内存 postgres 17280128 27504196 6876049 26001504 70.0 postgres: autovacuum launcher process 怀疑是服务器内存处理出现问题造成. 到服务器上杀掉该进程 ps -ewf|grep auto postgres 5821 5816 0 2010 ? 05:13:02 postgres: autovacuum launcher process postgres=# select * from pg_terminate_backend(5821); pg_terminate_backend ---------------------- t (1 row) 日志输出如下： 2011-02-14 17:47:07.905 CST,5821,4ccfbe6a.16bd,2,2010-11-02 15:31:54 CST,1/0,LOG,00000,"autovacuum launcher shutting down","" 2011-02-14 17:47:10.005 CST,15773,4d58fa1e.3d9d,1,2011-02-14 17:47:10 CST,"autovacuum launcher started","" autovacuum launcher的主进程为postgres进程，在被终结后自动产生. ps -ewf|grep auto postgres 15773 5816 0 17:47 ? 00:00:00 postgres: autovacuum launcher process 交换分区释放: free total used free shared buffers cached Mem: 24682828 7307256 17375572 0 10676 6525460 -/+ buffers/cache: 771120 23911708 Swap: 16779884 54836 16725048 PS输出注释: %mem %MEM ratio of the process’s resident set size to the physical memory on the machine,expressed as a percentage. (alias pmem). RSS RSS resident set size,the non-swapped physical memory that a task has used (in kiloBytes). (alias RSSize,rsz). RSSize RSS see RSS. (alias RSS,rsz). rsz RSZ see RSS. (alias RSS,RSSize). 从上面的解释来看autovacuum launcher 进程占据了约70%的不可交换物理内存.

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