通常习惯直接把ps里的RSS看做是进程使用的物理内存。 rss RSS resident set size, the non-swapped physical memory that a task has used
(in kiloBytes). (alias rssize, rsz).
随便在笔记本虚机上看一个oracle进程，居然有30M之巨 [oracle@server2 ~]$ ps aux | head -n 1; ps aux | grep LOCAL=YES| grep -v grep
USER PID %CPU %MEM VSZ
RSS TTY STAT START TIME COMMAND
oracle 2295 0.0 1.6 856044
30764 ? Ss 21:23 0:00 oracleorcl (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))
SQL> !ps -ef| grep LOCAL=NO| wc -l
1823 User CPU % Thrd Disk Memory Block
Process Name PID Name (12800%max) Cnt IOrate RSS/VSS On
--------------------------------------------------------------------------------
oraclePRODB2 17050 grid 0.0 1 0.0
226.5mb 241.9mb SOCKT
oraclePRODB2 7029 grid 0.0 1 0.0
216.6mb 218.9mb SOCKT
oraclePRODB2 16306 grid 0.0 1 0.0
227.8mb 239.3mb SOCKT
oraclePRODB2 17114 grid 0.1 1 0.0
224.3mb 243.7mb SOCKT
oraclePRODB2 15957 grid 0.0 1 0.0
226.5mb 240.2mb SOCKT
但是这台机器的 物理内存一个1T， SGA就固定400G，现在用户进程只用了447G，因此按进程上的RSS简单相加肯定是不准的。 Event Current Cumulative Current Rate Cum Rate High Rate
--------------------------------------------------------------------------------
Page Faults 858 4050 343.2 470.9 662.5
Page In 0 0 0.0 0.0 148.9
Page Out 0 0 0.0 0.0 0.0
KB Paged In 0kb 0kb 0.0 0.0 0.0
KB Paged Out 0kb 0kb 0.0 0.0 0.0
Reactivations 0 0 0.0 0.0 0.0
Deactivations 0 0 0.0 0.0 0.0
KB Deactivated 0kb 0kb 0.0 0.0 0.0
VM Reads 0 0 0.0 0.0 0.0
VM Writes 0 0 0.0 0.0 0.0
Total VM : 464.7gb Sys Mem : 104.9gb
User Mem: 447.8gb Phys Mem : 1023gb Active VM: 261.3gb Buf Cache: 0mb Free Mem: 455.8gb FileCache: 14.5gb
MemFS Blk Cnt: 0 MemFS Swp Cnt: 0
以进程17050为例,glance里显示226.5m。查看pga实际分配了3M SQL> select round(pga_alloc_mem/1024/1024, 2)||' (MB)' alloc_mb from v$process where spid = 17050; ALLOC_MB ----------------- 3.09 (MB) SQL> select round(sum(pga_alloc_mem)/1024/1024/1024, 2)||' (GB)' sum_alloc_mb from v$process; SUM_ALLOC_MB --------------------------------------------- 11.47 (GB) On HP-UX, for processes that use CPU time subsequent to midaemon startup, the resident memory is calculated as RSS = sum of private region pages + (sum of shared region pages / number of references) The number of references is a count of the number of attachments to the memory region. Attachments, for shared regions, may come from several processes sharing the same memory, a single process with multiple attachments, or combinations of these. This value is only updated when a process uses CPU.Thus, under memory pressure, this value may be higher than the actual amount of resident memory for processes which are idle because their memory pages may no longer be resident or the reference count for shared segments may have changed. 上面提到有两个原因会造成RSS显示远大于进程实际使用的内存 - RSS除了进程私有物理内存之外，还要加上[它所使用的共享内存大小 / 所有正在使用这个共享内存的进程数]。
- 由于RSS只有在进程使用CPU时才更新，如果进程idle了，就再也不会更新，永远是那么大。
因此每个进程最少200多M，应该就是通过SGA的400000 / 1823 = 219 算出来的。 来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/26239116/viewspace-1472417/，如需转载，请注明出处，否则将追究法律责任。