[systemd-devel] Memory in systemctl status

[Reindl Harald]

Am 27.09.20 um 14:08 schrieb Greg KH:
> On Sun, Sep 27, 2020 at 01:41:33PM +0200, Reindl Harald wrote:
>> Memory: 8.6G
>>
>> looks like there is a large part of os-caching included where i wonmder
>> how that's done because a file can be read by muliple processes /
>> services and is hopfefully only once cached
>>
>> however, that value makes little to no sense and if that's the same
>> value as accounted for "MemoryMax" it's plain wrong
>>
>> [root at arrakis:~]$ free
>>               total        used        free      shared  buff/cache
>> available
>> Mem:           15Gi       2.2Gi       585Mi       309Mi        12Gi
>>    12Gi
>> Swap:            0B          0B          0B
> 
> The kernel does this, it's nothing to do with systemd or anything else.
> 
> You can get "back" that memory for a short while if you really want it
> by doing:
> 	echo 3 > /proc/sys/vm/drop_caches
> 
> For more details, see https://www.linuxatemyram.com/

you completly miss the point and should not cut in the middle of a post!

Memory: 8.6G

*no* httpd don't consume 8.6GB RAM

the question is *why* systemd takes the os-cache into account of the
memory a service is using

[root at arrakis:~]$ systemctl status httpd.service
● httpd.service - Apache Webserver
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled;
vendor preset: disabled)
  Drop-In: /etc/systemd/system/httpd.service.d
           └─lockdown.conf
   Active: active (running) since Sun 2020-09-20 07:53:39 CEST; 1 weeks
0 days ago
  Process: 1935633 ExecReload=/usr/sbin/httpd $OPTIONS -k graceful
(code=exited, status=0/SUCCESS)
 Main PID: 713 (httpd)
    Tasks: 17 (limit: 1024)
   Memory: 8.6G
      CPU: 2h 8min 5.442s
   CGroup: /system.slice/httpd.service
           ├─    713 /usr/sbin/httpd -D FOREGROUND
           ├─2151772 /usr/sbin/httpd -D FOREGROUND
           ├─2151803 /usr/sbin/httpd -D FOREGROUND
           ├─2151805 /usr/sbin/httpd -D FOREGROUND
           ├─2152130 /usr/sbin/httpd -D FOREGROUND
           ├─2152132 /usr/sbin/httpd -D FOREGROUND
           ├─2152188 /usr/sbin/httpd -D FOREGROUND
           ├─2152189 /usr/sbin/httpd -D FOREGROUND
           ├─2152199 /usr/sbin/httpd -D FOREGROUND
           ├─2152211 /usr/sbin/httpd -D FOREGROUND
           ├─2152213 /usr/sbin/httpd -D FOREGROUND
           ├─2152214 /usr/sbin/httpd -D FOREGROUND
           ├─2152215 /usr/sbin/httpd -D FOREGROUND
           ├─2152217 /usr/sbin/httpd -D FOREGROUND
           ├─2152220 /usr/sbin/httpd -D FOREGROUND
           ├─2152756 /usr/sbin/httpd -D FOREGROUND
           └─2152886 /usr/sbin/httpd -D FOREGROUND