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cycle_thief.txt
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cycle_thief.stp - Track IRQ's and Other Processes Stealing Cycles from a Task Description: The cycle_thief.stp script instruments the scheduler and IRQ handler to determine which processes and interrupts are competing with the specified task for the cpu cycles. This script uses the '-c' or '-x' options to focus on a specific task. The script output the number of times the task migrates between processors, histograms showing the length of time on and off processor, lists of processes running while the task is off the processor, and the interrupts that occurred while the task was running. $ stap cycle_thief.stp task 0 migrated: 1 task 0 on processor (us): value |-------------------------------------------------- count 2 | 0 4 | 0 8 |@ 1 16 | 0 32 | 0 64 | 0 128 |@@@@@@@@ 8 256 |@ 1 512 | 0 1024 |@ 1 2048 |@@@@@@@@ 8 4096 |@@@@@@@@@@@ 11 8192 |@@ 2 16384 |@@ 2 32768 |@@@@@@@@@@@@ 12 65536 |@@@@@ 5 131072 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 30 262144 | 0 524288 | 0 task 0 off processor (us) value |-------------------------------------------------- count 1 | 0 2 | 0 4 |@@@@ 4 8 |@@@@@@@@@@@@@@@@@@@@@@@@@@@ 27 16 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 34 32 |@@@@ 4 64 |@@@@@ 5 128 |@@@@@ 5 256 | 0 512 |@ 1 1024 | 0 2048 | 0 other pids taking processor from task 0 PID count command 25145 33 stapio 19189 17 kworker/0:3 7 13 rcu_sched 22717 9 kworker/1:1 380 8 jbd2/dm-0-8 9 8 rcuos/1 570 6 kworker/0:1H 8 3 rcuos/0 478 3 systemd-journal 24747 3 kworker/0:1 491 2 systemd-udevd 19120 2 sshd 25142 2 stapio 615 1 alsactl 625 1 irqbalance 25144 1 stapio 31816 1 kworker/u4:1 25141 1 stap 724 1 NetworkManager 25143 1 systemd-udevd irq taking processor from task 0 irq count min(us) avg(us) max(us) 44 9 3 8 19 The output from running the script for ~10 seconds. The histograms provide a visual of the time a process spent on, or off. The sampled processes are listed below the histograms to give a sense of what was running at the time. As mentioned in the description, the script can be focused on a certain process with -c/-x. $ stap cycle_thief.stp -T 10 task 29018 migrated: 2 task 29018 on processor (us): value |-------------------------------------------------- count 2 | 0 4 | 0 8 |@ 1 16 | 0 32 |@ 1 64 |@ 1 128 | 0 256 |@ 1 512 | 0 1024 | 0 task 29018 off processor (us) value |-------------------------------------------------- count 2 | 0 4 | 0 8 |@ 1 16 |@ 1 32 | 0 64 | 0 ~ 2097152 | 0 4194304 | 0 8388608 |@ 1 16777216 | 0 33554432 | 0 other pids taking processor from task 29018 PID count command 0 41 swapper/0 19189 24 kworker/0:3 7 12 rcu_sched 8 8 rcuos/0 29002 5 kworker/0:0 380 4 jbd2/dm-0-8 570 3 kworker/0:1H 6 3 kworker/u4:0 491 2 systemd-udevd 29016 2 stapio 29017 1 systemd-udevd 478 1 systemd-journal 625 1 irqbalance 14 1 migration/1 irq taking processor from task 29018 irq count min(us) avg(us) max(us)