T4432: display load averages normalized for the number of CPU cores

1 files changed, 102 insertions, 0 deletions

diff --git a/python/vyos/cpu.py b/python/vyos/cpu.py
new file mode 100644
index 000000000..a0ef864be
--- /dev/null
+++ b/python/vyos/cpu.py
@@ -0,0 +1,102 @@
+#!/usr/bin/env python3
+# Copyright 2022 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Retrieves (or at least attempts to retrieve) the total number of real CPU cores
+installed in a Linux system.
+
+The issue of core count is complicated by existence of SMT, e.g. Intel's Hyper Threading.
+GNU nproc returns the number of LOGICAL cores,
+which is 2x of the real cores if SMT is enabled.
+
+The idea is to find all physical CPUs and add up their core counts.
+It has special cases for x86_64 and MAY work correctly on other architectures,
+but nothing is certain.
+"""
+
+import re
+
+
+def _read_cpuinfo():
+    with open('/proc/cpuinfo', 'r') as f:
+        return f.readlines()
+
+def _split_line(l):
+    l = l.strip()
+    parts = re.split(r'\s*:\s*', l)
+    return (parts[0], ":".join(parts[1:]))
+
+def _find_cpus(cpuinfo_lines):
+    # Make a dict because it's more convenient to work with later,
+    # when we need to find physicall distinct CPUs there.
+    cpus = {}
+
+    cpu_number = 0
+
+    for l in cpuinfo_lines:
+        key, value = _split_line(l)
+        if key == 'processor':
+            cpu_number = value
+            cpus[cpu_number] = {}
+        else:
+            cpus[cpu_number][key] = value
+
+    return cpus
+
+def _find_physical_cpus():
+    cpus = _find_cpus(_read_cpuinfo())
+
+    phys_cpus = {}
+
+    for num in cpus:
+        if 'physical id' in cpus[num]:
+            # On at least some architectures, CPUs in different sockets
+            # have different 'physical id' field, e.g. on x86_64.
+            phys_id = cpus[num]['physical id']
+            if phys_id not in phys_cpus:
+                phys_cpus[phys_id] = cpus[num]
+        else:
+            # On other architectures, e.g. on ARM, there's no such field.
+            # We just assume they are different CPUs,
+            # whether single core ones or cores of physical CPUs.
+            phys_cpus[num] = cpu[num]
+
+    return phys_cpus
+
+def get_cpus():
+    """ Returns a list of /proc/cpuinfo entries that belong to different CPUs.
+    """
+    cpus_dict = _find_physical_cpus()
+    return list(cpus_dict.values())
+
+def get_core_count():
+    """ Returns the total number of physical CPU cores
+        (even if Hyper-Threading or another SMT is enabled and has inflated
+        the number of cores in /proc/cpuinfo)
+    """
+    physical_cpus = _find_physical_cpus()
+
+    core_count = 0
+
+    for num in physical_cpus:
+        # Some architectures, e.g. x86_64, include a field for core count.
+        # Since we found unique physical CPU entries, we can sum their core counts.
+        if 'cpu cores' in physical_cpus[num]:
+            core_count += int(physical_cpus[num]['cpu cores'])
+        else:
+            core_count += 1
+
+    return core_count