Performance Tuning

Linux Kernel Version

  • Use the latest stable upstream Linux kernel for the best performance.

    • Despite claims of custom kernels providing enhanced performance, benchmarks show that in most cases they are still not as fast as the upstream Linux kernel. [1] The LTS Linux kernel is slower and does not support newer hardware compared to the latest stable version but it is more stable. [2]

  • Use at least Linux kernel 6.6 [3] to get the low latency benefits of the new EEVDF CPU scheduler. [4]

Minimize Writes

Introduction

By moving more writes into RAM, both (1) the lifespan of a storage device and (2) the speed of a computer will be faster.

Swap

  • Do not use a swap file. Instead, configure zram with lz4 compression and other optimized setings. Refer to zram.

    $ sudo -E ${EDITOR} /etc/sysctl.d/99-zram.conf
vm.swappiness = 180
vm.watermark_boost_factor = 0
vm.watermark_scale_factor = 125
vm.page-cluster = 1
$ sudo -E ${EDITOR} /etc/systemd/zram-generator.conf
[zram0]
compression-algorithm = lz4
zram-size = ram * 2
$ sudo systemctl enable systemd-zram-setup@zram0.service

Ephemeral Logs

Thes changes generally reduce the amount of logs for security and troubleshooting purposes. In exchange, a storage device will have a longer lifespan.

  • Use tmpfs as the file system for /tmp, /var/log, and /var/tmp mounts in /etc/fstab. Refer to ramfs and tmpfs.

  • Store journald logs in memory. Refer to journald configuration.

    $ sudo -E ${EDITOR} /etc/systemd/journald.conf
[Journal]
Storage=volatile

  • Use the mount options noatime,nodiratime in /etc/fstab. Refer to Mount Options.

Delay Writes

Delay storage writes to reduce the wear on the storage device’s lifespan. These changes can lead to data loss if there is a power outage.

  • Keep writes in RAM for much longer. Refer to Memory Caching.

    $ sudo -E ${EDITOR} /etc/sysctl.d/50-ram-write-cache.conf
vm.dirty_background_ratio = 40
vm.dirty_ratio = 80
vm.vfs_cache_pressure = 50

  • Increase the commit time (the interval before syncing writes to the storage device) to 5 minutes by using the mount option commit=300 in /etc/fstab. There may be noticeable lag or a system hang if the interval is too long or if the drive is too slow. Refer to Mount Options.

History

Bibliography

  1. “The Performance Impact From Different Arch Linux Kernel Flavors.” Phoronix. January 25, 2023. Accessed December 29, 2023. https://www.phoronix.com/review/arch-linux-kernels-2023

  2. “Why and How to install the LTS kernel in Arch Linux.” Average Linux User. August 23, 2018. Accessed December 29, 2023. https://averagelinuxuser.com/the-lts-kernel-in-arch-linux/

  3. “EEVDF Scheduler Merged For Linux 6.6, Intel Hybrid Cluster Scheduling Re-Introduced.” Phoronix. August 29, 2023. Accessed February 17, 2024. https://www.phoronix.com/news/Linux-6.6-EEVDF-Merged

  4. “An EEVDF CPU scheduler for Linux.” LWN.net. March 9, 2023. Accessed February 17, 2024. https://lwn.net/Articles/925371/