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This can result in an empty topology directory in sysfs, and requires in-kernel users to protect all uses with #ifdef - see <http://marc.info/?l=linux-netdev&m=120639033904472&w=2>. The documentation of CPU topology specifies what the defaults should be if only partial information is available from the hardware. So we can provide these defaults as a fallback. This patch: - Adds default definitions of the 4 topology macros to <linux/topology.h> - Changes drivers/base/topology.c to use the topology macros unconditionally and to cope with definitions that aren't lvalues - Updates documentation accordingly [ From: Andrew Morton <akpm@linux-foundation.org> - fold now-duplicated code - fix layout ] Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Cc: Vegard Nossum <vegard.nossum@gmail.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Chandra Seetharaman <sekharan@us.ibm.com> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Mike Travis <travis@sgi.com> Cc: Christoph Lameter <clameter@sgi.com> Cc: John Hawkes <hawkes@sgi.com> Cc: Zhang, Yanmin <yanmin.zhang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
34 lines
1.2 KiB
Plaintext
34 lines
1.2 KiB
Plaintext
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Export cpu topology info via sysfs. Items (attributes) are similar
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to /proc/cpuinfo.
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1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
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represent the physical package id of cpu X;
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2) /sys/devices/system/cpu/cpuX/topology/core_id:
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represent the cpu core id to cpu X;
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3) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
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represent the thread siblings to cpu X in the same core;
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4) /sys/devices/system/cpu/cpuX/topology/core_siblings:
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represent the thread siblings to cpu X in the same physical package;
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To implement it in an architecture-neutral way, a new source file,
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drivers/base/topology.c, is to export the 4 attributes.
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For an architecture to support this feature, it must define some of
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these macros in include/asm-XXX/topology.h:
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#define topology_physical_package_id(cpu)
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#define topology_core_id(cpu)
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#define topology_thread_siblings(cpu)
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#define topology_core_siblings(cpu)
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The type of **_id is int.
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The type of siblings is cpumask_t.
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To be consistent on all architectures, include/linux/topology.h
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provides default definitions for any of the above macros that are
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not defined by include/asm-XXX/topology.h:
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1) physical_package_id: -1
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2) core_id: 0
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3) thread_siblings: just the given CPU
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4) core_siblings: just the given CPU
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