Messages in this thread | | | Date | Thu, 16 Jan 2020 12:41:35 -0500 (EST) | From | Mathieu Desnoyers <> | Subject | [regression] cpuset: offlined CPUs removed from affinity masks |
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Hi,
I noticed the following regression with CONFIG_CPUSET=y. Note that I am not using cpusets at all (only using the root cpuset I'm given at boot), it's just configured in. I am currently working on a 5.2.5 kernel. I am simply combining use of taskset(1) (setting the affinity mask of a process) and cpu hotplug. The result is that with CONFIG_CPUSET=y, setting the affinity mask including an offline CPU number don't keep that CPU in the affinity mask, and it is never put back when the CPU comes back online. CONFIG_CPUSET=n behaves as expected, and puts back the CPU into the affinity mask reported to user-space when it comes back online.
* With CONFIG_CPUSET=y (unexpected behavior):
# echo 0 > /sys/devices/system/cpu/cpu1/online
% taskset 0x7 ./loop & % taskset -p $! pid 1341's current affinity mask: 5
# echo 1 > /sys/devices/system/cpu/cpu1/online
taskset -p $! pid 1341's current affinity mask: 5
kill $!
* With CONFIG_CPUSET=n (expected behavior):
(Offlining CPU, then start task)
# echo 0 > /sys/devices/system/cpu/cpu1/online
% taskset 0x7 ./loop & % taskset -p $! pid 1358's current affinity mask: 5
# echo 1 > /sys/devices/system/cpu/cpu1/online
taskset -p $! pid 1358's current affinity mask: 7
kill $!
Test system lscpu output:
Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 32 On-line CPU(s) list: 0-31 Thread(s) per core: 2 Core(s) per socket: 8 Socket(s): 2 NUMA node(s): 2 Vendor ID: GenuineIntel CPU family: 6 Model: 60 Model name: Intel Core Processor (Haswell, no TSX, IBRS) Stepping: 1 CPU MHz: 2399.996 BogoMIPS: 4799.99 Hypervisor vendor: KVM Virtualization type: full L1d cache: 32K L1i cache: 32K L2 cache: 4096K NUMA node0 CPU(s): 0-7,16-23 NUMA node1 CPU(s): 8-15,24-31 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp lm constant_tsc rep_good nopl cpuid tsc_known_freq pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm cpuid_fault invpcid_single pti ibrs ibpb fsgsbase bmi1 avx2 smep bmi2 erms invpcid xsaveopt
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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