Zram-swap-config

Like zram-config-0.5

zram-config-0.5 is a broken package that for many reasons should not be used. Zram-swap-config is an interim package until zram-config-0.5 is fixed in deploy and operation

Usefull for IoT / maker projects for reducing SD, Nand and Emmc block wear via write operations. Check the Swapiness-load-balancer branch for dynamic swappiness control. Works well in conjunction with https://github.com/StuartIanNaylor/zramdrive and https://github.com/StuartIanNaylor/log2zram

Menu

1. Install
2. Upgrade
3. Customize
4. It is working ?
5. Uninstall

Install

apt-get install git
git clone https://github.com/StuartIanNaylor/zram-swap-config
cd zram-swap-config
chmod +x install.sh && sudo ./install.sh
cd ..
rm -rf zram-swap-config

Upgrade

Run zram-swap-config-uninstall.sh from /usr/local/bin/ and start then start the new install.

Customize

variables :

In the file /etc/zram-swap-config.conf:

• MEM_FACTOR = Percentage of available ram to allocate to all zram swap devices which is divided equally by swap_devices number
• DRIVE_FACTOR = Virtual uncompressed zram drive size estimate approx alg compression ratio
• COMP_ALG lz4 is faster than lzo but some distro's show compile and operational difference and in use lzo depending on binary may be faster. Compression rates list below are minimums and generally far bigger in operation but dependent on content.
• SWAP_DEVICES = number of indivial drives sharing memeory provided by MEM_FACTOR each device support multiple streams 1 large drive is generally better
• SWAP_PRI = swap_priority for each drive 75 is a high order preference and should be well above other swap drives
• PAGE_CLUSTER default page cluster is 3 which caches fetches in batches of 8 and helps with HDD paging, with zram mem 0 forces single page fetches This can help reduce latency and increase performance
• SWAPPINESS default swappiness is 60 but with increased performance of zram swap 80 garners overall performance gain without excessive load Because zram uses compression load is created and even if minimal at intense load periods such as boot any extra load is unwanted Unfortunately there is no dynamic load balancing of swappiness as with zram in general operation SWAPINESS=100 will garner performance benefit If the overall load is reasonable at high load it will cause load to accumulate. If you check my repo there will also be a simple dynamic load based SWAPPINESS governor that will get of the hurdle of a static compromise on swappiness

# Configuration file for zram-swap-config (https://github.com/StuartIanNaylor/zram-swap-config) under GNU General Public License v3.0 license.
# This configuration file is read by the zram-swap-config service

# MEM_FACTOR = Percentage of available ram to allocate to all zram swap devices which is divided equally by swap_devices number
MEM_FACTOR=50
# DRIVE_FACTOR = Virtual uncompressed zram drive size estimate approx alg compression ratio 
DRIVE_FACTOR=210
# COMP_ALG lz4 is faster than lzo but some distro's show compile and operation difference and in use lzo depending on binary may be faster
COMP_ALG=lz4
# SWAP_DEVICES = number of indivial drives sharing memeory provided by MEM_FACTOR each device support multiple streams 1 large drive is generally better
SWAP_DEVICES=1
# SWAP_PRI = swap_priority for each drive 75 is a hig order preference and should be well above other swap drives
SWAP_PRI=75
# PAGE_CLUSTER default page cluster is 3 which caches fetches in batches of 8 and helps with HDD paging, with zram mem 0 forces single page fetches
# This can help reduce latency and increase performance
PAGE_CLUSTER=0
# SWAPPINESS default swappiness is 60 but with increased performance of zram swap 80 garners overall performance gain without excessive load
# Because zram uses compression load is created and even if minimal at intense load periods such as boot any extra load is unwanted
# Unfortunately there is no dynamic load balancing of swappiness as with zram in general operation SWAPINESS=100 will garner performance benefit
# If the overall load is reasonable at high load it will cause load to accumulate. 
SWAPPINESS=80
# If you check my repo there will also be a simple dynamic load branch based SWAPPINESS governor that will get of the hurdle of a static compromise on swappiness

It is working?

You can now check the mount folder in ram with (You will see lines with zram if working)

# zramctl
…
NAME       ALGORITHM DISKSIZE  DATA  COMPR TOTAL STREAMS MOUNTPOINT
/dev/zram0 lz4         455.1M    4K    65B    4K       1 [SWAP]
/dev/zram1               140M 17.7M 432.4K  680K       1 /var/log
…

# swapon
…
NAME       TYPE        SIZE USED PRIO
/dev/zram0 partition 455.1M   0B   75
/var/swap  file        100M   0B   -2
…
# free -m
…
              total        used        free      shared  buff/cache   available
Mem:            433          31         329           3          72         351
Swap:           555           0         555
…
# cat /proc/sys/vm/swappiness
…
80
…
# cat /proc/sys/vm/page-cluster
…
0
…
# sudo apt-get install stress
# stress --vm 3 --vm-bytes 256M --timeout 60s
…
stress: info: [861] dispatching hogs: 0 cpu, 0 io, 3 vm, 0 hdd
stress: info: [861] successful run completed in 60s

Any comp alg can be used for zram, zramctl unfortunately only has the text strings for lzo/lz4 so blank space is displayed. zstd kernel inclusion seems to have some politics attached. Check /proc/crypto for available.

You may wish to uninstall raspbian file swap services

sudo apt-get remove dphys-swapfile
or
disable
sudo systemctl disable dphys-swapfile

Uninstall

sudo chmod +x /usr/local/bin/zram-swap-config-uninstall.sh && sudo /usr/local/bin/zram-swap-config-uninstall.sh

Git Branches & Update

From the command line, enter cd <path_to_local_repo> so that you can enter commands for your repository. Enter git add --all at the command line to add the files or changes to the repository Enter git commit -m '<commit_message>' at the command line to commit new files/changes to the local repository. For the <commit_message> , you can enter anything that describes the changes you are committing. Enter git push at the command line to copy your files from your local repository to remote.