Why is only 11 GB used of my 12 GB swap file ?

[Sreyan Chakravarty]

Hi,

I have created my swap file using the command:

          dd if=/dev/zero of=/fedora.swap bs=1M count=12288 status=progress

So this should produce a 12 GB file right ?

I can confirm it does:

$  ls -lh /fedora.swap
-rw-------. 1 root root 12G Nov 27 20:23 /fedora.swap

So why is the swap memory in my system reported as 11 GB by the free
command  ?

$  free -h
                           total        used        free      shared
 buff/cache   available
Mem:          7.7Gi       1.4Gi       4.5Gi       394Mi       1.8Gi
5.6Gi
Swap:          11Gi          0B        11Gi


Why is it 11 GB ? Shouldn't it be 12 GB ?

Am I missing something?

What is the reason for this?
-- 
Regards,
Sreyan Chakravarty

[Jorge Fábregas]

On 11/27/20 1:19 PM, Sreyan Chakravarty wrote:
>  So why is the swap memory in my system reported as 11 GB by the free
>  command  ? 
Did you:


# mkswap /fedora.swap
# swapon /fedora.swap

...afterwards?

-- 
Jorge

[Sreyan Chakravarty]

On Fri, 27 Nov 2020, 10:58 pm Jorge Fábregas, <jorge.fabregas(a)gmail.com
>  
wrote:

>  Did you:
>
>
>  # mkswap /fedora.swap
>  # swapon /fedora.swap
>  
Yes.

>

[Jorge Fábregas]

On 11/27/20 1:31 PM, Sreyan Chakravarty wrote:
>  Yes.  
What does the following commands show?

# free --giga
# swapon -s

[Sreyan Chakravarty]

On Fri, Nov 27, 2020 at 11:13 PM Jorge Fábregas <jorge.fabregas(a)gmail.com&gt;
wrote:

>  What does the following commands show?
>
>  # free --giga
>  
              total        used        free      shared  buff/cache
available
Mem:              8           1           4           0           2
  5
Swap:            12           0          12


>  # swapon -s
>  
Filename Type Size Used Priority
/fedora.swap                           file     12582908 0 -2

Why are the outputs of free -h different from free --giga ?

Regards,
Sreyan Chakravarty

[Jorge Fábregas]

On 11/27/20 2:33 PM, Sreyan Chakravarty wrote:
>  Why are the outputs of free -h different from free --giga ? 
https://searchstorage.techtarget.com/definition/gibibyte-GiB

HTH,
Jorge

[Sreyan Chakravarty]

Thanks.

On Sat, 28 Nov 2020, 12:17 am Jorge Fábregas, <jorge.fabregas(a)gmail.com&gt;
wrote:

>  On 11/27/20 2:33 PM, Sreyan Chakravarty wrote:
>  > Why are the outputs of free -h different from free --giga ?
>
>  https://searchstorage.techtarget.com/definition/gibibyte-GiB
>
>  HTH,
>  Jorge
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[Roberto Ragusa]

On 11/27/20 6:43 PM, Jorge Fábregas wrote:
>  On 11/27/20 1:31 PM, Sreyan Chakravarty wrote:
> > Yes.
>  
>  What does the following commands show?
>  
>  # free --giga 
There is no point in using gigabytes, if the swap file was created as gibibytes.
Unless one wants to mess with things just to get a 12 as output.

The file was created as exactly 12GiB and the available swap is probably
very near 12GiB, with just a little loss caused by some metadata
included in the partition.

A better suggestion would be to not use such a huge units of measurements
that will obviously suffer from integer truncation. That 11 was probably
a 11.9 or 11.99 or (and I bet on this) 11.999.

I would use "free --mebi" instead.
The swap file was 12288 MiB. Let's see how much of that is available as swap.

Regards.

-- 
    Roberto Ragusa    mail at robertoragusa.it

Swap file in mebibytes

[David]

Mr. Ragusa,

Thank you very much for that suggestion.

Now I have a new topic to add to my bucket-list of things to have a better
grasp of.

I am still trying to decide if I need a swap file or how small can it be,
and or if I need a swap partition.

All of that is currently over my brain capacity.

I have 32 GB of fast RAM and play FreeCell pretty intensively LOL !

David Locklear
Arcola, Texas, USA



>  A better suggestion would be to not use such a huge units of
> measurements
>  
use "free --mebi"
>