Hello Every one

I have a query and confused on it
Let me explain it.

My goal is that I want to calculate memory utilization of apache.

Below is the output of Free command before starting apache service.

total used free shared buffers cached
Mem: 248 42 205 0 7 19
-/+ buffers/cache: 15 233
Swap: 298 0 298


And after starting the httpd service output of Free command

total used free shared buffers cached
Mem: 248 50 190 0 7 22
-/+ buffers/cache: 20 227
Swap: 298 0 298


It shows about 5MB increase in memroy (As show by buffers/cache: 20 227 line )


Now oput ut of top command

Mem: 254532k total, 60392k used, 194140k free, 8232k buffers
Swap: 305192k total, 0k used, 305192k free, 30532k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2778 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2779 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2780 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2781 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2782 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2783 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2784 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd
2785 apache 25 0 19444 9176 5900 S 0.0 3.6 0:00.00 httpd




This output show that their are 8 process of apache running and eache process using 9176 kilo byte memory. (as shown by RES field)


According to this memory usuage bye apche becomes about 73mb .

I am so much confuse on this .

Can any explain what is the actual memory usuage by apache

The RES memory is the code + data segments of the executable. These are probably mapped to the same physical pages for each Apache pages (certainly the code is, since it doesn't change between the Apache processes, so it only needs to exist once in physical memory). I suspect the executable itself is only taking up a few mwgabytes, but you can check with "size `which httpd`". It doesn't look like anything is apged out, so the rest of the discrepency is probably in buffers/cache. I would imagine Apache uses a lot of buffer and cache space since it is network and disk I/O intensive.