Hi, Adding Tejun and the cgroups mailing list in CC for this cpuset regression I reported last month. Thanks, Mathieu ----- On Jan 16, 2020, at 12:41 PM, Mathieu Desnoyers mathieu.desnoyers@xxxxxxxxxxxx wrote: > 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 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
