Esync removes wineserver overhead for synchronization objects. This increases performance for a lot of games, especially ones that rely heavily on multithreading.
A more detailed explanation can be found here.
Systems using Systemd 240 and newer are already compatible with Esync.
If you're unsure that your system is compatible, run the ulimit -Hn command. If the value printed is equal to or greater than 524288, then your system is Esync-compatible.
If your system is not Esync-compatible (ulimit -Hn, which prints the limit for number of opened files for a process, prints a value lower than 524288, like 4096), you have 2 different methods of solving this problem.
Which method is preferable depends on the distribution currently in use. Applying both methods should have no negative side effect.
Modifying Systemd configuration
This method applies to Ubuntu and other systems using systemd. You (with root privileges or sudo) need to edit both /etc/systemd/system.conf and /etc/systemd/user.conf by adding DefaultLimitNOFILE=524288. If DefaultLimitNOFILE= already exists in both system.conf and user.conf, add 524288 after = and make sure to uncomment the line (remove the # in the beginning of the line) to make it functional.
Once the files are edited, restart your computer for the changes to take effect. To verify if the limits were applied, run ulimit -Hn to see 524288 being reported.
If the value printed still says something like 4096, try the ulimits method below.
Modifying ulimits.conf
On Linux distributions not using Systemd or distributions using pam-limits.conf (Arch Linux, Fedora, Solus,... ), you (with root privileges or sudo) need to edit /etc/security/limits.conf.
Change username to your actual username. Once the file is edited, reboot for the changes to take effect, and verify by running ulimit -Hn to see the new limit (524288).
username hard nofile 524288
Using Esync Wine builds
Esync is enabled by default starting with Lutris 0.5.9 and all presently available Lutris Wine versions include Esync.