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commit: 00354a2443c1a0f7f64d55daadd52324868b085f |
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Author: Robin H. Johnson <robbat2 <AT> gentoo <DOT> org> |
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AuthorDate: Sat Feb 16 06:06:41 2019 +0000 |
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Commit: Robin H. Johnson <robbat2 <AT> gentoo <DOT> org> |
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CommitDate: Sat Feb 16 06:06:41 2019 +0000 |
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URL: https://gitweb.gentoo.org/proj/portage.git/commit/?id=00354a24 |
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|
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cpuinfo: use better available CPU calculation |
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|
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The existing portage.util.cpuinfo.get_cpu_count() behavior is wrong when |
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run in any environment where the cpuset is a subset of online CPUs. |
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|
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The solution recommended by the 'os.cpu_count()' help is to use: |
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len(os.sched_getaffinity(0)) |
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|
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This only works on line, so keep multiprocessing.cpu_count() as a |
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fallback. In newer version of Python, multiprocessing.cpu_count() is a |
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wrapper for os.cpu_count(). |
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|
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Reported-By: Daniel Robbins <drobbins <AT> funtoo.org> |
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Fixes: https://bugs.funtoo.org/browse/FL-6227 |
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Signed-off-by: Robin H. Johnson <robbat2 <AT> gentoo.org> |
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|
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lib/portage/util/cpuinfo.py | 33 +++++++++++++++++++++++++++++++-- |
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1 file changed, 31 insertions(+), 2 deletions(-) |
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|
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diff --git a/lib/portage/util/cpuinfo.py b/lib/portage/util/cpuinfo.py |
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index 669e707b5..9ab1c119d 100644 |
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--- a/lib/portage/util/cpuinfo.py |
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+++ b/lib/portage/util/cpuinfo.py |
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@@ -1,15 +1,44 @@ |
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-# Copyright 2015 Gentoo Foundation |
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+# Copyright 2015-2019 Gentoo Authors |
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# Distributed under the terms of the GNU General Public License v2 |
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|
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__all__ = ['get_cpu_count'] |
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|
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+# Before you set out to change this function, figure out what you're really |
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+# asking: |
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+# |
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+# - How many CPUs exist in this system (e.g. that the kernel is aware of?) |
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+# This is 'getconf _NPROCESSORS_CONF' / get_nprocs_conf(3) |
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+# In modern Linux, implemented by counting CPUs in /sys/devices/system/cpu/ |
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+# |
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+# - How many CPUs in this system are ONLINE right now? |
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+# This is 'getconf _NPROCESSORS_ONLN' / get_nprocs(3) |
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+# In modern Linux, implemented by parsing /sys/devices/system/cpu/online |
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+# |
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+# - How many CPUs are available to this program? |
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+# This is 'nproc' / sched_getaffinity(2), which is implemented in modern |
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+# Linux kernels by querying the kernel scheduler; This might not be available |
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+# in some non-Linux systems! |
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+# |
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+# - How many CPUs are available to this thread? |
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+# This is pthread_getaffinity_np(3) |
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+# |
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+# As a further warning, the results returned by this function can differ |
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+# between runs, if altered by the scheduler or other external factors. |
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|
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def get_cpu_count(): |
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""" |
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- Try to obtain the number of CPUs available. |
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+ Try to obtain the number of CPUs available to this process. |
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|
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@return: Number of CPUs or None if unable to obtain. |
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""" |
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+ try: |
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+ import os |
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+ # This was introduced in Python 3.3 only, but exists in Linux |
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+ # all the way back to the 2.5.8 kernel. |
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+ # This NOT available in FreeBSD! |
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+ return len(os.sched_getaffinity(0)) |
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+ except (ImportError, NotImplementedError, AttributeError): |
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+ pass |
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|
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try: |
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import multiprocessing |
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