workqueue: Add tools/workqueue/wq_dump.py which prints out workqueue configuration

Lack of visibility has always been a pain point for workqueues. While the
recently added wq_monitor.py improved the situation, it's still difficult to
understand what worker pools are active in the system, how workqueues map to
them and why. The lack of visibility into how workqueues are configured is
going to become more noticeable as workqueue improves locality awareness and
provides more mechanisms to customize locality related behaviors.

Now that the basic framework for more flexible locality support is in place,
this is a good time to improve the situation. This patch adds
tools/workqueues/wq_dump.py which prints out the topology configuration,
worker pools and how workqueues are mapped to pools. Read the command's help
message for more details.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2023-08-07 15:57:24 -10:00
parent 84193c0710
commit 7f7dc377a3
2 changed files with 225 additions and 0 deletions

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@ -347,6 +347,65 @@ Guidelines
level of locality in wq operations and work item execution.
Examining Configuration
=======================
Use tools/workqueue/wq_dump.py to examine unbound CPU affinity
configuration, worker pools and how workqueues map to the pools: ::
$ tools/workqueue/wq_dump.py
Affinity Scopes
===============
wq_unbound_cpumask=0000000f
NUMA
nr_pods 2
pod_cpus [0]=00000003 [1]=0000000c
pod_node [0]=0 [1]=1
cpu_pod [0]=0 [1]=0 [2]=1 [3]=1
SYSTEM
nr_pods 1
pod_cpus [0]=0000000f
pod_node [0]=-1
cpu_pod [0]=0 [1]=0 [2]=0 [3]=0
Worker Pools
============
pool[00] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 0
pool[01] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 0
pool[02] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 1
pool[03] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 1
pool[04] ref= 1 nice= 0 idle/workers= 4/ 4 cpu= 2
pool[05] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 2
pool[06] ref= 1 nice= 0 idle/workers= 3/ 3 cpu= 3
pool[07] ref= 1 nice=-20 idle/workers= 2/ 2 cpu= 3
pool[08] ref=42 nice= 0 idle/workers= 6/ 6 cpus=0000000f
pool[09] ref=28 nice= 0 idle/workers= 3/ 3 cpus=00000003
pool[10] ref=28 nice= 0 idle/workers= 17/ 17 cpus=0000000c
pool[11] ref= 1 nice=-20 idle/workers= 1/ 1 cpus=0000000f
pool[12] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=00000003
pool[13] ref= 2 nice=-20 idle/workers= 1/ 1 cpus=0000000c
Workqueue CPU -> pool
=====================
[ workqueue \ CPU 0 1 2 3 dfl]
events percpu 0 2 4 6
events_highpri percpu 1 3 5 7
events_long percpu 0 2 4 6
events_unbound unbound 9 9 10 10 8
events_freezable percpu 0 2 4 6
events_power_efficient percpu 0 2 4 6
events_freezable_power_ percpu 0 2 4 6
rcu_gp percpu 0 2 4 6
rcu_par_gp percpu 0 2 4 6
slub_flushwq percpu 0 2 4 6
netns ordered 8 8 8 8 8
...
See the command's help message for more info.
Monitoring
==========

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tools/workqueue/wq_dump.py Normal file
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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 show the current workqueue configuration. For more
info on drgn, visit https://github.com/osandov/drgn.
Affinity Scopes
===============
Shows the CPUs that can be used for unbound workqueues and how they will be
grouped by each available affinity type. For each type:
nr_pods number of CPU pods in the affinity type
pod_cpus CPUs in each pod
pod_node NUMA node for memory allocation for each pod
cpu_pod pod that each CPU is associated to
Worker Pools
============
Lists all worker pools indexed by their ID. For each pool:
ref number of pool_workqueue's associated with this pool
nice nice value of the worker threads in the pool
idle number of idle workers
workers number of all workers
cpu CPU the pool is associated with (per-cpu pool)
cpus CPUs the workers in the pool can run on (unbound pool)
Workqueue CPU -> pool
=====================
Lists all workqueues along with their type and worker pool association. For
each workqueue:
NAME TYPE POOL_ID...
NAME name of the workqueue
TYPE percpu, unbound or ordered
POOL_ID worker pool ID associated with each possible CPU
"""
import sys
import drgn
from drgn.helpers.linux.list import list_for_each_entry,list_empty
from drgn.helpers.linux.percpu import per_cpu_ptr
from drgn.helpers.linux.cpumask import for_each_cpu,for_each_possible_cpu
from drgn.helpers.linux.idr import idr_for_each
import argparse
parser = argparse.ArgumentParser(description=desc,
formatter_class=argparse.RawTextHelpFormatter)
args = parser.parse_args()
def err(s):
print(s, file=sys.stderr, flush=True)
sys.exit(1)
def cpumask_str(cpumask):
output = ""
base = 0
v = 0
for cpu in for_each_cpu(cpumask[0]):
while cpu - base >= 32:
output += f'{hex(v)} '
base += 32
v = 0
v |= 1 << (cpu - base)
if v > 0:
output += f'{v:08x}'
return output.strip()
worker_pool_idr = prog['worker_pool_idr']
workqueues = prog['workqueues']
wq_unbound_cpumask = prog['wq_unbound_cpumask']
wq_pod_types = prog['wq_pod_types']
WQ_UNBOUND = prog['WQ_UNBOUND']
WQ_ORDERED = prog['__WQ_ORDERED']
WQ_MEM_RECLAIM = prog['WQ_MEM_RECLAIM']
WQ_AFFN_NUMA = prog['WQ_AFFN_NUMA']
WQ_AFFN_SYSTEM = prog['WQ_AFFN_SYSTEM']
print('Affinity Scopes')
print('===============')
print(f'wq_unbound_cpumask={cpumask_str(wq_unbound_cpumask)}')
def print_pod_type(pt):
print(f' nr_pods {pt.nr_pods.value_()}')
print(' pod_cpus', end='')
for pod in range(pt.nr_pods):
print(f' [{pod}]={cpumask_str(pt.pod_cpus[pod])}', end='')
print('')
print(' pod_node', end='')
for pod in range(pt.nr_pods):
print(f' [{pod}]={pt.pod_node[pod].value_()}', end='')
print('')
print(f' cpu_pod ', end='')
for cpu in for_each_possible_cpu(prog):
print(f' [{cpu}]={pt.cpu_pod[cpu].value_()}', end='')
print('')
print('')
print('NUMA')
print_pod_type(wq_pod_types[WQ_AFFN_NUMA])
print('')
print('SYSTEM')
print_pod_type(wq_pod_types[WQ_AFFN_SYSTEM])
print('')
print('Worker Pools')
print('============')
max_pool_id_len = 0
max_ref_len = 0
for pi, pool in idr_for_each(worker_pool_idr):
pool = drgn.Object(prog, 'struct worker_pool', address=pool)
max_pool_id_len = max(max_pool_id_len, len(f'{pi}'))
max_ref_len = max(max_ref_len, len(f'{pool.refcnt.value_()}'))
for pi, pool in idr_for_each(worker_pool_idr):
pool = drgn.Object(prog, 'struct worker_pool', address=pool)
print(f'pool[{pi:0{max_pool_id_len}}] ref={pool.refcnt.value_():{max_ref_len}} nice={pool.attrs.nice.value_():3} ', end='')
print(f'idle/workers={pool.nr_idle.value_():3}/{pool.nr_workers.value_():3} ', end='')
if pool.cpu >= 0:
print(f'cpu={pool.cpu.value_():3}', end='')
else:
print(f'cpus={cpumask_str(pool.attrs.cpumask)}', end='')
print('')
print('')
print('Workqueue CPU -> pool')
print('=====================')
print('[ workqueue \ CPU ', end='')
for cpu in for_each_possible_cpu(prog):
print(f' {cpu:{max_pool_id_len}}', end='')
print(' dfl]')
for wq in list_for_each_entry('struct workqueue_struct', workqueues.address_of_(), 'list'):
print(f'{wq.name.string_().decode()[-24:]:24}', end='')
if wq.flags & WQ_UNBOUND:
if wq.flags & WQ_ORDERED:
print(' ordered', end='')
else:
print(' unbound', end='')
else:
print(' percpu ', end='')
for cpu in for_each_possible_cpu(prog):
pool_id = per_cpu_ptr(wq.cpu_pwq, cpu)[0].pool.id.value_()
field_len = max(len(str(cpu)), max_pool_id_len)
print(f' {pool_id:{field_len}}', end='')
if wq.flags & WQ_UNBOUND:
print(f' {wq.dfl_pwq.pool.id.value_():{max_pool_id_len}}', end='')
print('')