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List:       qubes-users
Subject:    Re: [EXT] [qubes-users] Re: Is swap necessary?
From:       Ulrich Windl <Ulrich.Windl () rz ! uni-regensburg ! de>
Date:       2021-05-26 15:38:32
Message-ID: dc596ea7-c16e-ee0b-ead5-ef9ab55a5a0a () rz ! uni-regensburg ! de
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On 5/19/21 5:43 PM, TheGardner wrote:
> For me, it would be necessary, if you're running Qubes with 4-8GB of 
> RAM. But with 16,32 or even 64 GB of RAM a swap partition may be useless...

What about the "swappiness" kernel parameter? Here I see 
vm.swappiness=60 (default)

Having 16GB RAM and only 5 VMs running, no paging happened, even after I 
had set swappiness to 90 in Dom0:
[root@dom0 master]# free
               total        used        free      shared  buff/cache 
available
Mem:        3962388      817404     2410848       13412      734136 
2950516
Swap:      10485756           0    10485756


According to https://linuxhint.com/understanding_vm_swappiness/:
* 0: swap is disable
* 1: minimum amount of swapping without disabling it entirely
* 10: recommended value to improve performance when sufficient memory 
exists in a system
* 100: aggressive swapping

So I even set swappiness to 100, just top see what happens, and I still 
did not see any paging.

Even when starting three additional VMs, I could not see paging in Dom0:
[root@dom0 master]# vmstat 5
procs -----------memory---------- ---swap-- -----io---- -system-- 
------cpu-----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy 
id wa st
  0  0      0 2406852  55696 681864    0    0   272   331 1101 1033  1 
1 97  0  1
  0  0      0 2406592  55696 681932    0    0    26   198 5320 5075  1 
1 97  0  1
  0  0      0 2406576  55704 681940    0    0    13   103 5164 4973  1 
1 97  0  1
  0  0      0 2406624  55704 681860    0    0    13   122 5217 5015  1 
1 97  0  1
  0  0      0 2405616  55708 681876    0    0    13   139 7042 6530  1 
1 96  0  1
  0  0      0 2406144  55716 681888    0    0    38   283 7819 7319  2 
1 95  0  2
  1  0      0 2408128  55716 681924    0    0     1   118 7081 6661  1 
1 96  0  1
  1  0      0 2291836  55836 682396    0    0    79   366 8030 7576  7 
6 83  0  3
  0  0      0 2388740  54800 692632    0    0 20717  2839 14237 12176  4 
  5 81  0  9
  3  0      0 2268800  54916 694556    0    0 72948  6978 22038 21880  7 
10 69  0 14
  1  0      0 2332968  54916 704920    0    0 12738 12858 13951 12536  6 
  6 71  0 17
  2  0      0 2259164  56068 706068    0    0 12377  5766 13037 12304 10 
  9 64  1 17
  1  0      0 2263504  55040 717512    0    0 47908  9822 17386 16391  3 
  6 75  0 15
  3  0      0 1950336  55048 718884    0    0 50536 14435 20932 20627  4 
  6 69  1 21
  0  0      0 1789084  55056 719504    0    0 22490  6858 12711 12202  2 
  3 84  0 10
  0  0      0 1821772  55064 719532    0    0   275   433 6988 6579  3 
2 93  0  2
  1  0      0 1814452  55072 719496    0    0   230   918 5477 5370  1 
1 94  0  3
  0  0      0 1712640  55080 719660    0    0  4551 18286 8909 8085  2 
3 86  0  9
  0  0      0 2131492  56152 709116    0    0  1826  5031 10883 9946  5 
  8 72  3 12
  4  0      0 2259808  56164 698804    0    0  1322  7122 9417 8659  2 
3 88  0  6
  0  0      0 2333696  56224 698156    0    0  1862  2295 9031 8399  4 
8 76  4  7
  0  0      0 2362572  56284 686708    0    0   676  1020 7809 7022  4 
8 75  7  5
  0  0      0 2383836  56296 686484    0    0    13   374 5142 4777  2 
1 96  0  1
  0  0      0 2384740  56304 686464    0    0     0   218 5131 4880  1 
1 97  0  1
  0  0      0 2385496  56304 686372    0    0     0   124 4637 4471  1 
1 97  0  1
^C

Regards,
Ulrich

> 
> abra...@protonmail.com schrieb am Mittwoch, 19. Mai 2021 um 10:28:48 UTC+2:
> 
> The Qubes installer says swap is important. I did a Google search
> and it turned out that Qubes hardly even uses swap. Specifically, I
> found this:
> https://www.reddit.com/r/Qubes/comments/86evqe/swap_is_useless_on_qubes/dz32iof/?context=8&depth=9
>  <https://www.reddit.com/r/Qubes/comments/86evqe/swap_is_useless_on_qubes/dz32iof/?context=8&depth=9>
>  
> 
> Is it at all important to install Qubes with a swap partition?
> Currently I have it running without swap.
> 
> 
> Sent with ProtonMail Secure Email.
> 
> 
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