top中内存相关的解释

       n: %MEM  --  Memory usage (RES)
          A task's currently used share of available physical memory.

       o: VIRT  --  Virtual Image (kb)
          The total amount of virtual memory used by the task.  It includes all code, data and shared libraries plus pages that
          have been swapped out. (Note: you can define the STATSIZE=1 environment variable and the VIRT will be calculated from
          the /proc/#/state VmSize field.)

          VIRT = SWAP + RES.

       p: SWAP  --  Swapped size (kb)
          The swapped out portion of a task's total virtual memory image.

       q: RES  --  Resident size (kb)
          The non-swapped physical memory a task has used.

          RES = CODE + DATA.

       r: CODE  --  Code size (kb)
          The amount of physical memory devoted to executable code, also known as the 'text resident set' size or TRS.

       s: DATA  --  Data+Stack size (kb)
          The amount of physical memory devoted to other than executable code, also known as the 'data resident  set'  size  or
          DRS.

       t: SHR  --  Shared Mem size (kb)
          The  amount  of  shared memory used by a task.  It simply reflects memory that could be potentially shared with other
          processes.

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