Awesome
memavaild
Improve responsiveness during heavy swapping: keep amount of available memory.
"If you actually tried to use the memory it says in MemAvailable, you may very well already get bad side effects as the kernel needs to reclaim memory used for other purposes (file caches, mmap'ed executables, heap, …). Depending on the workload, this may already cause the system to start thrashing."
Default behavior: the control groups specified in the config (user.slice
and system.slice
) are swapped out when MemAvailable
is low by reducing memory.high
(values change dynamically). memavaild
tries to keep about 3% available memory.
Effects: tasks are performed at less I/O and memory pressure (and this may be detected by PSI metrics). At the same time, performance may be increased in tasks that requires heavy swapping, especially in I/O bound tasks. Using memavaild
has no effect without swap space.
Requirements
- Python 3.3+
- systemd with unified cgroup hierarchy
How to enable unified cgroup hierarchy
Unified cgroup hierarchy is enabled by default on Fedora 31+. On other distros pass systemd.unified_cgroup_hierarchy=1
to the kernel boot cmdline.
Known problems
- The documentation is terrible (no config keys description, for example);
- The ZFS ARC cache is memory-reclaimable, like the Linux buffer cache. However, in contrast to the buffer cache, it currently does not count to MemAvailable (see openzfs/zfs#10255). Don't use
memavaild
with ZFS; - Seems like
memavaild
violates the second rule:memavaild
manipulates the attributes of cgroups created by systemd (memavaild
changesmemory.high
values).
Install
For Arch Linux there's an AUR package
Use your favorite AUR helper. For example,
$ yay -S memavaild
$ sudo systemctl enable --now memavaild.service
memavaild-git is also available.
To install on Debian and Ubuntu-based systems:
It's easy to build a deb package with the latest git snapshot. Install build dependencies:
$ sudo apt install make fakeroot
Clone the latest git snapshot and run the build script to build the package:
$ git clone https://github.com/hakavlad/memavaild.git && cd memavaild
$ deb/build.sh
Install the package:
$ sudo apt install --reinstall ./deb/package.deb
Start and enable memavaild.service
after installing the package:
$ sudo systemctl enable --now memavaild.service
On other distros:
Install:
$ git clone https://github.com/hakavlad/memavaild.git && cd memavaild
$ sudo make install
$ sudo systemctl enable --now memavaild.service
Uninstall:
$ sudo make uninstall
How to configure
Edit the config (/etc/memavaild.conf
or /usr/local/etc/memavaild.conf
) and restart the service.
Demo
stress -m 9 --vm-bytes 99G
without full freezing (with swap on zram): https://www.youtube.com/watch?v=DJq00pEt4xg. This is an old demo that demonstrates how memavaild can keep available memory.stress -m 8 --vm-bytes 32G
with no freeze:prelockd
+memavaild
+nohang-desktop
+zram
, system on HDD: https://www.youtube.com/watch?v=veY606v57Hk