Comment # 2 on bug 1222946 from Takashi Iwai

The default value is hardcoded to 128 even in the latest upstream code, and I
see no big gain to have an extra kernel config for defining it when an easy
tuning knob with sysctl is already present.  I bet the suggestion to the
upstream would be declined by that reason, too.

You can statically set the value in /etc/sysctl.d/* instead.  e.g. unison
package may contain such a sysctl snippet.