Enable fsync and esync#10
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The L4S kernel backports futex_waitv (syscall 449), so Proton fsync works on the Tegra X1 4.9 kernel despite the "requires 5.x+" note. Enable it for the faster in-game synchronisation path. Also enable esync as a fallback: Wine selects fsync first when the kernel supports it, so esync (and its older dxvk caveat) only comes into play when fsync is unavailable. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
Flip the Wine sync env vars in
files/steam/launch-steam.shto enable fsync (and esync as a fallback):PROTON_NO_FSYNC=1→0WINEESYNC=0→1,PROTON_NO_ESYNC=1→0Why fsync works on the 4.9 kernel
The comment said fsync "requires Kernel 5.x+", which is why it was off. The L4S kernel backports
futex_waitv(syscall 449) — the upstreambf69bad38cf6primitive that Proton's fsync uses — into the Tegra X1 4.9 kernel. So fsync's kernel dependency is satisfied and Proton can use the fast vectored-futex sync path instead of falling back to slower server-side sync. This is a measurable win in CPU-bound games.About esync and the dxvk caveat
The previous comment noted esync "crashes dxvk and only works with wined3d". That stays true as a fallback path, but Wine picks fsync first whenever the kernel supports it (which it now does on L4S), so esync is only ever selected when fsync is unavailable. Enabling it gives a graceful fallback without changing behaviour on the L4S kernel, where fsync wins.
PROTON_NO_NTSYNC=1is left untouched — ntsync needs a 6.12+ driver that isn't backported.Test
On an L4S device the kernel exposes
sys_futex_waitv(kallsyms / syscall 449); with these flags Proton initialises in fsync mode rather than falling back. ntsync remains disabled.