[Mageia-discuss] File systems ?

[AL13N]

> On Friday 01 Jun 2012 17:22 my mailbox was graced by a message from David
> W.
> Hodgins who wrote:
>> > I run a script based on df to check the total HD use on my box.
>> > After installing Mageia 2 it gives impossible results, which I
>> attribute
>> > to DF now showing filesystems which I cannot find referenced in the
>> File
>> > Hierarchy Standard, like rootfs, devtmpfs or (several) tmpfs (mounted
>> in
>> > separate locations).
>
>> They are tmpfs filesystems, which by definition means they exist in ram
>> only.
>
> I wonder how they can exist in RAM given the total size of the tmpfs
> partitions is almost double the installed RAM of the computer.

tmpfs partitions are always shared in memory, they only use in memory what
is used. the available size is actually the maximum tmpfs partitions (in
total) can allocate from memory (and standard this is 50% of RAM).

this has been so for as long as tmpfs exists, which is decades really.

cgroup is a new kernel feature that allows grouping of processes (Control
Groups), killing the control group will kill all the processes in the
group. and it can be used to set process limits for the whole group.