I collected some perf data for further analysis. I run a simple arithmetic multi-core benchmark. The benchmark is 100% CPU bound - it adds 2 integers.
perf record java -jar target/benchmarks.jar org.ttnr.pmato.e2.cpumem.ArithmeticsBenchmark.add -wi 0 -i 40 -t 4 -f 1 # JMH version: 1.21 # VM version: JDK 1.8.0_181, Java HotSpot(TM) 64-Bit Server VM, 25.181-b13 # VM invoker: /opt/jdk1.8.0_181/jre/bin/java # VM options: <none> # Warmup: <none> # Measurement: 40 iterations, 1 s each # Timeout: 10 min per iteration # Threads: 4 threads, will synchronize iterations # Benchmark mode: Average time, time/op # Benchmark: org.ttnr.pmato.e2.cpumem.ArithmeticsBenchmark.add # Run progress: 0,00% complete, ETA 00:00:40 # Fork: 1 of 1 Iteration 1: 2,246 ±(99.9%) 0,648 ns/op // <------- 3.5+ GHz when started Iteration 2: 2,181 ±(99.9%) 0,196 ns/op Iteration 3: 2,262 ±(99.9%) 2,673 ns/op Iteration 4: 2,296 ±(99.9%) 2,751 ns/op Iteration 5: 3,004 ±(99.9%) 3,518 ns/op Iteration 6: 5,468 ±(99.9%) 0,159 ns/op // <------- sudden performance drop Iteration 7: 6,372 ±(99.9%) 0,620 ns/op // <------- now 1.3-1.5 GHz Iteration 8: 6,389 ±(99.9%) 4,850 ns/op Iteration 9: 5,363 ±(99.9%) 0,223 ns/op Iteration 10: 5,174 ±(99.9%) 0,584 ns/op Iteration 11: 5,093 ±(99.9%) 0,414 ns/op Iteration 12: 5,069 ±(99.9%) 0,127 ns/op Iteration 13: 5,070 ±(99.9%) 0,559 ns/op Iteration 14: 4,927 ±(99.9%) 0,080 ns/op Iteration 15: 5,045 ±(99.9%) 0,033 ns/op Iteration 16: 5,052 ±(99.9%) 0,162 ns/op Iteration 17: 4,964 ±(99.9%) 0,063 ns/op Iteration 18: 4,979 ±(99.9%) 0,058 ns/op Iteration 19: 4,992 ±(99.9%) 0,147 ns/op Iteration 20: 4,955 ±(99.9%) 0,083 ns/op Iteration 21: 5,061 ±(99.9%) 0,462 ns/op Iteration 22: 5,004 ±(99.9%) 0,264 ns/op Iteration 23: 4,966 ±(99.9%) 0,207 ns/op Iteration 24: 4,950 ±(99.9%) 0,125 ns/op Iteration 25: 4,925 ±(99.9%) 0,553 ns/op Iteration 26: 4,961 ±(99.9%) 0,138 ns/op Iteration 27: 4,921 ±(99.9%) 0,188 ns/op Iteration 28: 4,980 ±(99.9%) 0,372 ns/op Iteration 29: 4,899 ±(99.9%) 0,119 ns/op Iteration 30: 4,884 ±(99.9%) 0,314 ns/op Iteration 31: 4,878 ±(99.9%) 0,194 ns/op Iteration 32: 4,962 ±(99.9%) 0,997 ns/op Iteration 33: 4,958 ±(99.9%) 0,280 ns/op Iteration 34: 4,889 ±(99.9%) 0,162 ns/op Iteration 35: 5,018 ±(99.9%) 0,201 ns/op Iteration 36: 5,002 ±(99.9%) 0,229 ns/op Iteration 37: 4,927 ±(99.9%) 0,088 ns/op Iteration 38: 4,935 ±(99.9%) 0,114 ns/op Iteration 39: 4,976 ±(99.9%) 0,284 ns/op Iteration 40: 4,925 ±(99.9%) 0,128 ns/op Result "org.ttnr.pmato.e2.cpumem.ArithmeticsBenchmark.add": 4,748 ±(99.9%) 0,541 ns/op [Average] (min, avg, max) = (2,181, 4,748, 6,389), stdev = 0,962 CI (99.9%): [4,207, 5,289] (assumes normal distribution) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1797802 Title: Erratic behavior of intel pstate CPU frequency control Status in linux package in Ubuntu: Triaged Bug description: I noticed that sometimes my Ubuntu 18.10 system feels sluggish. The other times everything works fine. I don't know what triggers this weird state. Suspend / resume? Maybe. At first I thought this was maybe just a "perception issue", but then when the sluggishness happened again, I fired up i7z and it looks that CPU frequency almost never got over ~1600 MHz, But my CPU is perfectly capable of going up to 4000 MHz! I tried to fix it by setting echo 80 > /sys/devices/system/cpu/intel_pstate/min_perf_pct echo 80 > /sys/devices/system/cpu/intel_pstate/max_perf_pct I hoped I would force the CPU into almost max performance state this way. And indeed, once I ran these commands, i7z showed steady 3100+ MHz on all cores. Then something weird happened - when I run some mild load on the CPU, like just starting the IDE, during the startup the frequency ** dropped back to about 800-1600 MHz ** and returned to 3100 MHz after the load was gone (IDE loaded). The CPU core temperatures shown by sensors / i7z are ok and typically at about 40-50 C when this slowdown happens, so this doesn't look like thermal throttling. Any ideas? ProblemType: Bug DistroRelease: Ubuntu 18.10 Package: linux-image-4.18.0-10-generic 4.18.0-10.11 ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12 Uname: Linux 4.18.0-10-generic x86_64 ApportVersion: 2.20.10-0ubuntu13 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: pkolaczk 3281 F.... pulseaudio /dev/snd/pcmC0D0c: pkolaczk 3281 F...m pulseaudio CurrentDesktop: ubuntu:GNOME Date: Sun Oct 14 22:16:50 2018 DistributionChannelDescriptor: # This is a distribution channel descriptor # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor canonical-oem-somerville-xenial-amd64-20160624-2 HibernationDevice: RESUME=UUID=4836842e-0116-43c4-98b4-7a56427f81f1 InstallationDate: Installed on 2017-04-12 (549 days ago) InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47 MachineType: Dell Inc. Precision 5520 ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=pl_PL.UTF-8 SHELL=/bin/bash ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.18.0-10-generic root=UUID=7f76b1f0-8fef-41cc-86a2-99e554cb4d40 ro acpi_rev_override quiet splash iwlwifi.power_save=1 crashkernel=384M-:128M crashkernel=384M-:128M vt.handoff=1 RelatedPackageVersions: linux-restricted-modules-4.18.0-10-generic N/A linux-backports-modules-4.18.0-10-generic N/A linux-firmware 1.175 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 07/24/2018 dmi.bios.vendor: Dell Inc. dmi.bios.version: 1.11.0 dmi.board.name: 06X96V dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvr1.11.0:bd07/24/2018:svnDellInc.:pnPrecision5520:pvr:rvnDellInc.:rn06X96V:rvrA00:cvnDellInc.:ct10:cvr: dmi.product.family: Precision dmi.product.name: Precision 5520 dmi.product.sku: 07BF dmi.sys.vendor: Dell Inc. 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