Public bug reported:
Using zram-config on a system with a sufficiently high count of CPUs
causes the systemd service to fail. The reason being that there is a cap
on the amount of swap devices that can be allocated. Zram is properly
allocated, but the systemd service fails since some devices cannot be
allocated. Below is the output of the service.
The fix should be simple enough (but I'm not proficient with git patches
yet). The script at /usr/bin/init-zram-swapping currently takes the
number of CPUs and creates this many devices to enable parallelization.
The simplest fix would be to set a max number of devices.
An alternative would be to use a smaller number of devices, but enable
multiple threads on each device. My understanding is that this is now
possible, but I'm not sure which method is more performant.
...
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635155]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635155]: no label,
UUID=e340a051-f250-4d5c-b43a-8ba8c711dc14
Sep 09 08:39:42 ubuntu-server kernel: Adding 1545208k swap on /dev/zram25.
Priority:5 extents:1 across:1545208k SSFS
Sep 09 08:39:42 ubuntu-server kernel: zram26: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635175]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635175]: no label,
UUID=95e21e29-4626-4780-a162-88e06c606171
Sep 09 08:39:42 ubuntu-server kernel: Adding 1545208k swap on /dev/zram26.
Priority:5 extents:1 across:1545208k SSFS
Sep 09 08:39:42 ubuntu-server kernel: zram27: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635192]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635192]: no label,
UUID=c927bbd5-c446-438e-acc9-b5ce9960ccdc
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635193]: swapon: /dev/zram27:
swapon failed: Operation not permitted
Sep 09 08:39:42 ubuntu-server kernel: zram28: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635196]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635196]: no label,
UUID=3561d65c-a821-40e7-af6c-48752bce7522
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635198]: swapon: /dev/zram28:
swapon failed: Operation not permitted
Sep 09 08:39:42 ubuntu-server kernel: zram29: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635200]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635200]: no label,
UUID=41bd94f8-bdd2-43dd-b68f-e54062d70849
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635205]: swapon: /dev/zram29:
swapon failed: Operation not permitted
Sep 09 08:39:42 ubuntu-server kernel: zram30: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635209]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635209]: no label,
UUID=44e288ac-9492-409f-933c-41772adb907c
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635212]: swapon: /dev/zram30:
swapon failed: Operation not permitted
Sep 09 08:39:42 ubuntu-server kernel: zram31: detected capacity change from 0
to 1582297088
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635216]: Setting up swapspace
version 1, size = 1.5 GiB (1582292992 b>
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635216]: no label,
UUID=98669a26-7e16-4359-a535-c71532629f93
Sep 09 08:39:42 ubuntu-server init-zram-swapping[1635218]: swapon: /dev/zram31:
swapon failed: Operation not permitted
Sep 09 08:39:42 ubuntu-server systemd[1]: zram-config.service: Main process
exited, code=exited, status=255/EXCEPTION
System Config:
❯ lscpu
...
CPU(s): 32
On-line CPU(s) list: 0-31
Thread(s) per core: 2
Core(s) per socket: 8
Socket(s): 2
NUMA node(s): 2
...
Model name: Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz
** Affects: zram-config (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1895002
Title:
zram-config attempts to allocate more devices than permitted
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