The current one (rtirq-20140413) doesn't fetch any longer.
proaudio overlay is not maintained by gentoo proaudio team, check layman's repositories.xml
commit dc990c2ce3f52b90873d6e5dbf5bb04823860ba7 (HEAD -> master, origin/master, origin/HEAD) Author: Karl Linden <karl.j.linden@gmail.com> AuthorDate: Tue May 31 08:00:47 2016 +0200 Commit: Patrice Clement <monsieurp@gentoo.org> CommitDate: Tue May 31 07:07:36 2016 +0000 sys-process/rtirq: Initial commit. A crucial part of professional realtime audio is low latency. rtirq sets realtime priorities and scheduling policies for desired IRQ threads on boot. Without rtirq you would need to set these priorities yourself after each boot or live with sound dropouts. See also [1]. Gentoo-Bug: https://bugs.gentoo.org/566678 Closes: https://github.com/gentoo/gentoo/pull/1554 Package-Manager: portage-2.3.0_rc1 Signed-off-by: Patrice Clement <monsieurp@gentoo.org> [1]: http://alsa.opensrc.org/Rtirq sys-process/rtirq/Manifest | 1 + sys-process/rtirq/files/rtirq | 29 +++++++++++++++++++++++++++++ sys-process/rtirq/metadata.xml | 12 ++++++++++++ sys-process/rtirq/rtirq-20150216.ebuild | 42 ++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 84 insertions(+) create mode 100644 sys-process/rtirq/Manifest create mode 100644 sys-process/rtirq/files/rtirq create mode 100644 sys-process/rtirq/metadata.xml create mode 100644 sys-process/rtirq/rtirq-20150216.ebuild