tools/rcu/rcu-cbs.py

   1 #!/usr/bin/env drgn
   2 # SPDX-License-Identifier: GPL-2.0+
   3 #
   4 # Dump out the number of RCU callbacks outstanding.
   5 #
   6 # On older kernels having multiple flavors of RCU, this dumps out the
   7 # number of callbacks for the most heavily used flavor.
   8 #
   9 # Usage: sudo drgn rcu-cbs.py
  10 #
  11 # Copyright (C) 2021 Facebook, Inc.
  12 #
  13 # Authors: Paul E. McKenney <paulmck@kernel.org>
  14
  15 import sys
  16 import drgn
  17 from drgn import NULL, Object
  18 from drgn.helpers.linux import *
  19
  20 def get_rdp0(prog):
  21         try:
  22                 rdp0 = prog.variable('rcu_preempt_data', 'kernel/rcu/tree.c');
  23         except LookupError:
  24                 rdp0 = NULL;
  25
  26         if rdp0 == NULL:
  27                 try:
  28                         rdp0 = prog.variable('rcu_sched_data',
  29                                              'kernel/rcu/tree.c');
  30                 except LookupError:
  31                         rdp0 = NULL;
  32
  33         if rdp0 == NULL:
  34                 rdp0 = prog.variable('rcu_data', 'kernel/rcu/tree.c');
  35         return rdp0.address_of_();
  36
  37 rdp0 = get_rdp0(prog);
  38
  39 # Sum up RCU callbacks.
  40 sum = 0;
  41 for cpu in for_each_possible_cpu(prog):
  42         rdp = per_cpu_ptr(rdp0, cpu);
  43         len = rdp.cblist.len.value_();
  44         # print("CPU " + str(cpu) + " RCU callbacks: " + str(len));
  45         sum += len;
  46 print("Number of RCU callbacks in flight: " + str(sum));