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e5bd61e82b
This commit adds an rcu-cbs.py drgn script that computes the number of RCU callbacks waiting to be invoked. This information can be helpful when managing systems that are short of memory and that have software components that make heavy use of RCU, for example, by opening and closing files in tight loops. (But please note that there are almost always better ways to get your job done than by opening and closing files in tight loops.) Reported-by: Richard Weinberger <richard@nod.at> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
46 lines
1.1 KiB
Python
46 lines
1.1 KiB
Python
#!/usr/bin/env drgn
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# SPDX-License-Identifier: GPL-2.0+
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#
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# Dump out the number of RCU callbacks outstanding.
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#
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# On older kernels having multiple flavors of RCU, this dumps out the
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# number of callbacks for the most heavily used flavor.
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#
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# Usage: sudo drgn rcu-cbs.py
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#
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# Copyright (C) 2021 Facebook, Inc.
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#
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# Authors: Paul E. McKenney <paulmck@kernel.org>
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import sys
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import drgn
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from drgn import NULL, Object
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from drgn.helpers.linux import *
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def get_rdp0(prog):
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try:
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rdp0 = prog.variable('rcu_preempt_data', 'kernel/rcu/tree.c');
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except LookupError:
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rdp0 = NULL;
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if rdp0 == NULL:
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try:
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rdp0 = prog.variable('rcu_sched_data',
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'kernel/rcu/tree.c');
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except LookupError:
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rdp0 = NULL;
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if rdp0 == NULL:
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rdp0 = prog.variable('rcu_data', 'kernel/rcu/tree.c');
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return rdp0.address_of_();
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rdp0 = get_rdp0(prog);
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# Sum up RCU callbacks.
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sum = 0;
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for cpu in for_each_possible_cpu(prog):
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rdp = per_cpu_ptr(rdp0, cpu);
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len = rdp.cblist.len.value_();
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# print("CPU " + str(cpu) + " RCU callbacks: " + str(len));
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sum += len;
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print("Number of RCU callbacks in flight: " + str(sum));
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