Precached is written in Rust and utilizes the Linux Netlink connector interface to monitor the system for process events. It can act upon such events via multiple means. E.g. it is able to pre-fault pages into memory, to speed up loading of programs and increase the perceived overall 'snappiness' of the system. Additionally it supports offline prefetching of the most often used programs while the system is idle.
$ yay -Sy precached $ sudo dnf copr enable x3n0m0rph59/precached
$ sudo dnf install precached $ sudo add-apt-repository ppa:x3n0m0rph59/precached
$ sudo apt update && sudo apt install precached $ git clone https://gitlab.com/X3n0m0rph59/precached.git
$ cd precached/
$ cargo build --release
# ... copy files ... $ sudo systemctl enable --now precached.service
$ sudo systemctl enable --now precached-prime-caches.timer
$ systemctl --user enable --now precached-trigger.servicePrecached tries to tackle some of the long standing performance issues of the Linux desktop:
- The system has unused (free) memory directly after boot-up. Therefore programs take a longer time to start up, cache cold start is way slower than cache hot start
- A Cron-Job evicts many important pages from the page cache. The system feels sluggish afterwards and won't recover for a long time
- The system has unused (free) memory after a "memory hog" process quit. The system reacts sluggish until the caches are primed again
You can read about Linux's memory management here: https://www.linuxatemyram.com/index.html
You have a reasonably fast CPU and a slow disk drive (and an ample amount of RAM) installed in your system, then you may see a performance improvement by using precached. The larger the speed difference between the CPU (fast) and the I/O subsystem (slow), the more you gain by running precached.
- You have a fast NVMe SSD drive
- You have less than ~2GBs of RAM installed (and want to use a modern Linux desktop)
If any of the above is true for your system, then you aren't likely to get a noticeable improvement out of using precached.
The preliminary benchmarks that we took are looking very promising already. We used the current development version of precached (as of 2017-10-30) and ran some benchmarks on it:
The benchmarks confirmed that precached is able to speed up load times of mid-sized and huge applications on Linux. We nearly achieve cache hot load times on first run (after system boot-up) of applications like e.g. LibreOffice and Firefox. After a memory hog process exited we need a short amount of idle time (roughly ~30 secs) to re-prime the caches, after that we achieve cache hot load times again. We did not discover any corner cases at which the system performed significantly worse than without precached running. The system feels much more ‘snappier’ even directly after login. Boot-up is slowed down somewhat though, since we read approximately 2GB of additional data into the RAM cache (in our test setup). This happens with a raised nice level and mostly during the GDM greeter’s password prompt and thereafter. We are investigating the possibility to move the offline prefetch phase somewhat further into the startup process to achieve even faster boot times (delayed prefetching).
- Possibly implement fork-bomb mitigation
- Markov-chain based prefetching
- ...
We are actively looking for contributions! Besides from code contributions, we could especially well use:
- Text translations
- Documentation authors
- Issue triaging
So please feel free to participate!
If you are new to Open Source software, you may want to read How to Contribute
precached - Copyright (C) 2017-2020 the precached developers