Isn't timerfd the default under-the-hood implementation of the "soft" (the default) timer in FS for some years now? In other words, it's quite surprising this param had any effect at all. Are you sure it did it? What are your kernel, glibc (ldd --version) and FS versions?

From: Stanislav Sinyagin
Sent: Thursday, September 21, 2017 16:55
To: Freeswitch Users Help
Subject: Re: [Freeswitch-users] Session recording performance

that's right, loading mod_timerfd, and setting in the SIP profile
    <param name="rtp-timer-name" value="timerfd"/>

has eliminated the problem, and now all outbound RTP has jitter below 1ms.