fsync testing instructions

If you run games with Proton, you might want to test fsync! For more details, refer to this announcement.


If you know how to build the kernel, the testing branch is over there:

https://gitlab.collabora.com/krisman/linux/commits/futex-wait-multiple-master


Arch Linux

A linux-fsync package is available on the AUR at:

https://aur.archlinux.org/pkgbase/linux-fsync/

An Arch repository with pre-built packages is also available, see pinned comments on the AUR page for more information.

Ubuntu

We're maintaining PPAs for Ubuntu 18.04[launchpad.net] and Ubuntu 19.04[launchpad.net]. It's recommended to ppa-purge any other PPAs that include the kernel, like our SteamVR PPA.

After adding the PPA, installing `linux-mfutex-valve` and rebooting into our kernel should be the only step needed.

For example, to start testing on Ubuntu 18.04:



Mostly we are trying to make sure all games work fine with fsync; a slight CPU use reduction might be observed during testing.

If using Proton 4.11, fsync is enabled by default if the right kernel support is detected. You should see console messages in the form of:


To narrow down any new issues, the PROTON_NO_FSYNC=1 variable can be set to revert to esync even when an fsync-capable kernel is installed.

If you can reproduce a crash or performance regression that consistently goes away with PROTON_NO_FSYNC=1, please report it in the dedicated fsync issue[github.com].

Post any performance results with 4.11 and fsync toggled on/off to the performance results issue[github.com].