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Since kernel version 4.9.0 BPF stopped working in a KVM guest. The problem are calls to perf_event_open with CPU identifiers which do not exist (ENODEV). The root cause for this is that the current code assumes ascending numbered CPUs. However, this is not always the case (e.g. CPU hotplugging). This patch introduces the get_online_cpus() and get_possible_cpus() helper functions and uses the appropriate function for iterations over CPUs. The BPF_MAP_TYPE_PERF_EVENT_ARRAY map contains now an entry for each possible CPU instead of for each online CPU. Fixes: iovisor#893 Signed-off-by: Andreas Gerstmayr <[email protected]>
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/* | ||
* Copyright (c) 2016 Catalysts GmbH | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* https://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
#include <fstream> | ||
#include <sstream> | ||
#include "common.h" | ||
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namespace ebpf { | ||
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std::vector<int> read_cpu_range(std::string path) { | ||
std::ifstream cpus_range_stream { path }; | ||
std::vector<int> cpus; | ||
std::string cpu_range; | ||
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while (std::getline(cpus_range_stream, cpu_range, ',')) { | ||
std::size_t rangeop = cpu_range.find('-'); | ||
if (rangeop == std::string::npos) { | ||
cpus.push_back(std::stoi(cpu_range)); | ||
} | ||
else { | ||
int start = std::stoi(cpu_range.substr(0, rangeop)); | ||
int end = std::stoi(cpu_range.substr(rangeop + 1)); | ||
for (int i = start; i <= end; i++) | ||
cpus.push_back(i); | ||
} | ||
} | ||
return cpus; | ||
} | ||
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std::vector<int> get_online_cpus() { | ||
return read_cpu_range("/sys/devices/system/cpu/online"); | ||
} | ||
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std::vector<int> get_possible_cpus() { | ||
return read_cpu_range("/sys/devices/system/cpu/possible"); | ||
} | ||
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} // namespace ebpf |
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# Copyright 2016 Catalysts GmbH | ||
# | ||
# Licensed under the Apache License, Version 2.0 (the "License"); | ||
# you may not use this file except in compliance with the License. | ||
# You may obtain a copy of the License at | ||
# | ||
# https://www.apache.org/licenses/LICENSE-2.0 | ||
# | ||
# Unless required by applicable law or agreed to in writing, software | ||
# distributed under the License is distributed on an "AS IS" BASIS, | ||
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
# See the License for the specific language governing permissions and | ||
# limitations under the License. | ||
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def _read_cpu_range(path): | ||
cpus = [] | ||
with open(path, 'r') as f: | ||
cpus_range_str = f.read() | ||
for cpu_range in cpus_range_str.split(','): | ||
rangeop = cpu_range.find('-') | ||
if rangeop == -1: | ||
cpus.append(int(cpu_range)) | ||
else: | ||
start = int(cpu_range[:rangeop]) | ||
end = int(cpu_range[rangeop+1:]) | ||
cpus.extend(range(start, end+1)) | ||
return cpus | ||
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def get_online_cpus(): | ||
return _read_cpu_range('/sys/devices/system/cpu/online') | ||
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def get_possible_cpus(): | ||
return _read_cpu_range('/sys/devices/system/cpu/possible') |
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#!/usr/bin/python | ||
# Copyright (c) Catalysts GmbH | ||
# Licensed under the Apache License, Version 2.0 (the "License") | ||
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from bcc.utils import get_online_cpus | ||
import multiprocessing | ||
import unittest | ||
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class TestUtils(unittest.TestCase): | ||
def test_get_online_cpus(self): | ||
online_cpus = get_online_cpus() | ||
num_cores = multiprocessing.cpu_count() | ||
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self.assertEqual(len(online_cpus), num_cores) | ||
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if __name__ == "__main__": | ||
unittest.main() |