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9b07115f4a
cgroupv1 CPU quotas are not considered, as those are now legacy (RHEL7 era), and are more complex/inefficient to parse. Tested in coreutils on Fedora 42 as detailed in tests/test-nproc.c * lib/nproc.c (cgroup2_mount): Identify the cgroup2 mount point, first at the common location for efficiency, resorting to searching mount points otherwise. (get_cgroup2_cpu_quota): Walk cgroup2 quotas for the current process, returning the lowest integer number of CPUs configured. (cpu_quota): On Linux return the cgroupv2 CPU quota if the currrent scheduler honors it. Otherwise return ULONG_MAX. (num_processors): Clamp the return to <= quota. * m4/nproc.m4: Add a check for mntent.h. * tests/test-nproc.c: Document how cgroup CPU quotas were tested.
66 lines
1.7 KiB
C
66 lines
1.7 KiB
C
/*
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nproc honors cgroup v2 CPU quotas
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and was tested in coreutils on a Fedora 42 system as follows:
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# Note we honor a limit anywhere in /proc/self/cgroup hierarchy
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# so apply settings below in the parent cgroup of the current process
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$ nested_cgroup=/sys/fs/cgroup/$(dirname $(cut -d/ -f2- /proc/self/cgroup))
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$ echo $nested_cgroup
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/sys/fs/cgroup/user.slice/user-1001.slice/user@1001.service/app.slice
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# This test system has 4 CPUs
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$ src/nproc
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4
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# Behave like MAX (1, (int)round(quota/period))
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$ echo "100000 100000" > $nested_cgroup/cpu.max
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$ src/nproc
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1
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$ echo "90000 100000" > $nested_cgroup/cpu.max
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$ src/nproc
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1
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$ echo "140000 100000" > $nested_cgroup/cpu.max
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$ src/nproc
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1
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$ echo "150000 100000" > $nested_cgroup/cpu.max
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$ src/nproc
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2
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# Ensure NPROC_ALL takes precedence
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$ echo "100000 100000" > $nested_cgroup/cpu.max
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$ src/nproc --all
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4
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# Ensure OMP env vars have appropriate precedence
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$ echo "200000 100000" > $nested_cgroup/cpu.max
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$ OMP_NUM_THREADS=10 src/nproc
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10
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$ OMP_THREAD_LIMIT=10 src/nproc
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2
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# Ensure quota only reduces
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$ echo "500000 100000" > $nested_cgroup/cpu.max
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$ src/nproc
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4
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# Restore system to unlimited
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$ echo "max 100000" > $nested_cgroup/cpu.max
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# Test quota in root hierarchy
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$ podman run --cpus=2 -i --rm fedora:latest /tmp/nproc
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2
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$ podman run --cpus=1.5 -i --rm fedora:latest /tmp/nproc
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2
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$ podman run --cpus=1.4 -i --rm fedora:latest /tmp/nproc
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1
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$ podman run --cpus=100 -i --rm fedora:latest /tmp/nproc
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4
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# Docker is similar to podman, but explicitly limits max allowable
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$ docker run --cpus=1.4 -i --rm fedora:latest /tmp/nproc
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1
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$ docker run --cpus=100 -i --rm fedora:latest /tmp/nproc
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docker: Error response from daemon:
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range of CPUs is from 0.01 to 4.00, as there are only 4 CPUs
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*/
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