OpenCloudOS-Kernel/tools/workqueue/wq_monitor.py

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#!/usr/bin/env drgn
#
# Copyright (C) 2023 Tejun Heo <tj@kernel.org>
# Copyright (C) 2023 Meta Platforms, Inc. and affiliates.
desc = """
This is a drgn script to monitor workqueues. For more info on drgn, visit
https://github.com/osandov/drgn.
total Total number of work items executed by the workqueue.
infl The number of currently in-flight work items.
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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CPUitsv The number of times a concurrency-managed work item hogged CPU
longer than the threshold (workqueue.cpu_intensive_thresh_us)
and got excluded from concurrency management to avoid stalling
other work items.
CMwake The number of concurrency-management wake-ups while executing a
work item of the workqueue.
mayday The number of times the rescuer was requested while waiting for
new worker creation.
rescued The number of work items executed by the rescuer.
"""
import sys
import signal
import os
import re
import time
import json
import drgn
from drgn.helpers.linux.list import list_for_each_entry,list_empty
from drgn.helpers.linux.cpumask import for_each_possible_cpu
import argparse
parser = argparse.ArgumentParser(description=desc,
formatter_class=argparse.RawTextHelpFormatter)
parser.add_argument('workqueue', metavar='REGEX', nargs='*',
help='Target workqueue name patterns (all if empty)')
parser.add_argument('-i', '--interval', metavar='SECS', type=float, default=1,
help='Monitoring interval (0 to print once and exit)')
parser.add_argument('-j', '--json', action='store_true',
help='Output in json')
args = parser.parse_args()
def err(s):
print(s, file=sys.stderr, flush=True)
sys.exit(1)
workqueues = prog['workqueues']
WQ_UNBOUND = prog['WQ_UNBOUND']
WQ_MEM_RECLAIM = prog['WQ_MEM_RECLAIM']
PWQ_STAT_STARTED = prog['PWQ_STAT_STARTED'] # work items started execution
PWQ_STAT_COMPLETED = prog['PWQ_STAT_COMPLETED'] # work items completed execution
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
2023-05-18 11:02:08 +08:00
PWQ_STAT_CPU_INTENSIVE = prog['PWQ_STAT_CPU_INTENSIVE'] # wq_cpu_intensive_thresh_us violations
PWQ_STAT_CM_WAKEUP = prog['PWQ_STAT_CM_WAKEUP'] # concurrency-management worker wakeups
PWQ_STAT_MAYDAY = prog['PWQ_STAT_MAYDAY'] # maydays to rescuer
PWQ_STAT_RESCUED = prog['PWQ_STAT_RESCUED'] # linked work items executed by rescuer
PWQ_NR_STATS = prog['PWQ_NR_STATS']
class WqStats:
def __init__(self, wq):
self.name = wq.name.string_().decode()
self.unbound = wq.flags & WQ_UNBOUND != 0
self.mem_reclaim = wq.flags & WQ_MEM_RECLAIM != 0
self.stats = [0] * PWQ_NR_STATS
for pwq in list_for_each_entry('struct pool_workqueue', wq.pwqs.address_of_(), 'pwqs_node'):
for i in range(PWQ_NR_STATS):
self.stats[i] += int(pwq.stats[i])
def dict(self, now):
return { 'timestamp' : now,
'name' : self.name,
'unbound' : self.unbound,
'mem_reclaim' : self.mem_reclaim,
'started' : self.stats[PWQ_STAT_STARTED],
'completed' : self.stats[PWQ_STAT_COMPLETED],
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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'cpu_intensive' : self.stats[PWQ_STAT_CPU_INTENSIVE],
'cm_wakeup' : self.stats[PWQ_STAT_CM_WAKEUP],
'mayday' : self.stats[PWQ_STAT_MAYDAY],
'rescued' : self.stats[PWQ_STAT_RESCUED], }
def table_header_str():
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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return f'{"":>24} {"total":>8} {"infl":>5} '\
f'{"CPUitsv":>7} {"CMwake":>7} {"mayday":>7} {"rescued":>7}'
def table_row_str(self):
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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cpu_intensive = '-'
cm_wakeup = '-'
mayday = '-'
rescued = '-'
if not self.unbound:
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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cpu_intensive = str(self.stats[PWQ_STAT_CPU_INTENSIVE])
cm_wakeup = str(self.stats[PWQ_STAT_CM_WAKEUP])
if self.mem_reclaim:
mayday = str(self.stats[PWQ_STAT_MAYDAY])
rescued = str(self.stats[PWQ_STAT_RESCUED])
out = f'{self.name[-24:]:24} ' \
f'{self.stats[PWQ_STAT_STARTED]:8} ' \
f'{max(self.stats[PWQ_STAT_STARTED] - self.stats[PWQ_STAT_COMPLETED], 0):5} ' \
workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE If a per-cpu work item hogs the CPU, it can prevent other work items from starting through concurrency management. A per-cpu workqueue which intends to host such CPU-hogging work items can choose to not participate in concurrency management by setting %WQ_CPU_INTENSIVE; however, this can be error-prone and difficult to debug when missed. This patch adds an automatic CPU usage based detection. If a concurrency-managed work item consumes more CPU time than the threshold (10ms by default) continuously without intervening sleeps, wq_worker_tick() which is called from scheduler_tick() will detect the condition and automatically mark it CPU_INTENSIVE. The mechanism isn't foolproof: * Detection depends on tick hitting the work item. Getting preempted at the right timings may allow a violating work item to evade detection at least temporarily. * nohz_full CPUs may not be running ticks and thus can fail detection. * Even when detection is working, the 10ms detection delays can add up if many CPU-hogging work items are queued at the same time. However, in vast majority of cases, this should be able to detect violations reliably and provide reasonable protection with a small increase in code complexity. If some work items trigger this condition repeatedly, the bigger problem likely is the CPU being saturated with such per-cpu work items and the solution would be making them UNBOUND. The next patch will add a debug mechanism to help spot such cases. v4: Documentation for workqueue.cpu_intensive_thresh_us added to kernel-parameters.txt. v3: Switch to use wq_worker_tick() instead of hooking into preemptions as suggested by Peter. v2: Lai pointed out that wq_worker_stopping() also needs to be called from preemption and rtlock paths and an earlier patch was updated accordingly. This patch adds a comment describing the risk of infinte recursions and how they're avoided. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
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f'{cpu_intensive:>7} ' \
f'{cm_wakeup:>7} ' \
f'{mayday:>7} ' \
f'{rescued:>7} '
return out.rstrip(':')
exit_req = False
def sigint_handler(signr, frame):
global exit_req
exit_req = True
def main():
# handle args
table_fmt = not args.json
interval = args.interval
re_str = None
if args.workqueue:
for r in args.workqueue:
if re_str is None:
re_str = r
else:
re_str += '|' + r
filter_re = re.compile(re_str) if re_str else None
# monitoring loop
signal.signal(signal.SIGINT, sigint_handler)
while not exit_req:
now = time.time()
if table_fmt:
print()
print(WqStats.table_header_str())
for wq in list_for_each_entry('struct workqueue_struct', workqueues.address_of_(), 'list'):
stats = WqStats(wq)
if filter_re and not filter_re.search(stats.name):
continue
if table_fmt:
print(stats.table_row_str())
else:
print(stats.dict(now))
if interval == 0:
break
time.sleep(interval)
if __name__ == "__main__":
main()