Re: shared_buffers vs Linux file cache

Thanks very much, Glyn, Jeff, and Tom. That was very clearly explained.

A related case, see the following top dump. The Postgres process is using 87g residential memory, which I thought was the physical memory consumed by a process that can't be shared with others. While, the free+cached is about 155gb. But, (87 + 155) is bigger than the total available 198g RAM. Does this mean some of the residential memory used by Postgres is actually shareable to others?

   

>> Mem:  198311880k total, 183836408k used, 14475472k free, 8388k buffers
>> Swap:  4194300k total,   314284k used,  3880016k free, 141105408k cached
>>
>>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+ COMMAND
>> 15338 postgres  20   0 97.9g  87g  87g S  0.3 46.4  21:47.44 
>> postgres: checkpointer process
>> 27473 postgres  20   0 98.1g  29g  29g S  0.0 15.8   2:14.93 
>> postgres: xxxx idle
>>  4710 postgres  20   0 98.1g  24g  23g S  0.0 12.7   1:17.41 
>> postgres: xxxx idle 

>> 26587 postgres 20 0 98.0g 15g 15g S 0.0 8.0 1:21.24