Latest upload to Groovy has the fix. Testing the backported version does not show notable regression in clock_nanosleep's CPU utilization (on a Lenovo Yoga X1 Gen 2 laptop): root@ff-glibc:~# cat > test-nanosleep.c #include void main() { struct timespec req = {0, 0}; for (int i = 0; i < 100000; i++){ clock_nanosleep(CLOCK_REALTIME, 0, &req, NULL); } } root@ff-glibc:~# gcc test-nanosleep.c -o test-nanosleep root@ff-glibc:~# time ./test-nanosleep real 0m6.110s user 0m0.291s sys 0m0.567s root@ff-glibc:~# time ./test-nanosleep real 0m6.078s user 0m0.243s sys 0m0.614s root@ff-glibc:~# time ./test-nanosleep real 0m6.095s user 0m0.226s sys 0m0.637s root@ff-glibc:~# apt ^C root@ff-glibc:~# apt update Hit:1 http://archive.ubuntu.com/ubuntu focal InRelease Get:2 http://archive.ubuntu.com/ubuntu focal-updates InRelease [111 kB] Get:3 http://security.ubuntu.com/ubuntu focal-security InRelease [107 kB] Get:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB] Get:5 http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages [8628 kB] Get:6 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages [148 kB] Get:7 http://archive.ubuntu.com/ubuntu focal/universe Translation-en [5124 kB] Get:8 http://archive.ubuntu.com/ubuntu focal/universe amd64 c-n-f Metadata [265 kB] Get:9 http://security.ubuntu.com/ubuntu focal-security/universe amd64 Packages [44.4 kB] Get:10 http://archive.ubuntu.com/ubuntu focal/multiverse amd64 Packages [144 kB] Get:11 http://archive.ubuntu.com/ubuntu focal/multiverse Translation-en [104 kB] Get:12 http://security.ubuntu.com/ubuntu focal-security/universe Translation-en [23.6 kB] Get:13 http://archive.ubuntu.com/ubuntu focal/multiverse amd64 c-n-f Metadata [9136 B] Get:14 http://security.ubuntu.com/ubuntu focal-security/universe amd64 c-n-f Metadata [1832 B] Get:15 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages [315 kB] Get:16 http://security.ubuntu.com/ubuntu focal-security/multiverse amd64 Packages [1172 B] Get:17 http://security.ubuntu.com/ubuntu focal-security/multiverse Translation-en [540 B] Get:18 http://security.ubuntu.com/ubuntu focal-security/multiverse amd64 c-n-f Metadata [116 B] Get:19 http://archive.ubuntu.com/ubuntu focal-updates/main Translation-en [118 kB] Get:20 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 c-n-f Metadata [7964 B] Get:21 http://archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages [146 kB] Get:22 http://archive.ubuntu.com/ubuntu focal-updates/universe Translation-en [73.9 kB] Get:23 http://archive.ubuntu.com/ubuntu focal-updates/universe amd64 c-n-f Metadata [4920 B] Get:24 http://archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 Packages [11.6 kB] Get:25 http://archive.ubuntu.com/ubuntu focal-updates/multiverse Translation-en [3892 B] Get:26 http://archive.ubuntu.com/ubuntu focal-updates/multiverse amd64 c-n-f Metadata [480 B] Get:27 http://archive.ubuntu.com/ubuntu focal-backports/main amd64 c-n-f Metadata [112 B] Get:28 http://archive.ubuntu.com/ubuntu focal-backports/restricted amd64 c-n-f Metadata [116 B] Get:29 http://archive.ubuntu.com/ubuntu focal-backports/universe amd64 Packages [3096 B] Get:30 http://archive.ubuntu.com/ubuntu focal-backports/universe Translation-en [1448 B] Get:31 http://archive.ubuntu.com/ubuntu focal-backports/universe amd64 c-n-f Metadata [224 B] Get:32 http://archive.ubuntu.com/ubuntu focal-backports/multiverse amd64 c-n-f Metadata [116 B] Fetched 15.5 MB in 7s (2197 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done 1 package can be upgraded. Run 'apt list --upgradable' to see it. root@ff-glibc:~# add-apt-repository ppa:rbalint/scratch2 More info: https://launchpad.net/~rbalint/+archive/ubuntu/scratch2 Press [ENTER] to continue or Ctrl-c to cancel adding it. Hit:1 http://archive.ubuntu.com/ubuntu focal InRelease Hit:2 http://archive.ubuntu.com/ubuntu focal-updates InRelease Hit:3 http://archive.ubuntu.com/ubuntu focal-backports InRelease Hit:4 http://security.ubuntu.com/ubuntu focal-security InRelease Get:5 http://ppa.launchpad.net/rbalint/scratch2/ubuntu focal InRelease [18.1 kB] Get:6 http://ppa.launchpad.net/rbalint/scratch2/ubuntu focal/main amd64 Packages [3396 B] Get:7 http://ppa.launchpad.net/rbalint/scratch2/ubuntu focal/main Translation-en [2076 B] Fetched 23.5 kB in 1s (15.9 kB/s) Reading package lists... Done root@ff-glibc:~# time ./test-nanosleep real 0m6.080s user 0m0.229s sys 0m0.614s root@ff-glibc:~# for i in $(seq 3); do time ./test-nanosleep ; done real 0m6.456s user 0m0.145s sys 0m0.413s real 0m5.934s user 0m0.131s sys 0m0.377s real 0m5.689s user 0m0.141s sys 0m0.273s root@ff-glibc:~# root@ff-glibc:~# root@ff-glibc:~# for i in $(seq 3); do time ./test-nanosleep ; done ^C real 0m3.682s user 0m0.142s sys 0m0.387s root@ff-glibc:~# for i in $(seq 5); do time ./test-nanosleep ; done real 0m6.091s user 0m0.281s sys 0m0.596s real 0m6.059s user 0m0.245s sys 0m0.599s real 0m6.066s user 0m0.226s sys 0m0.581s real 0m6.065s user 0m0.284s sys 0m0.574s real 0m6.101s user 0m0.287s sys 0m0.587s