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fb2ff9fa72
>From Power10 processors onwards, each chip has 2 hemispheres. For LPARs
running on PowerVM Hypervisor, hypervisor determines the allocation of
CPU groups to each LPAR, resulting in two LPARs with the same number of
CPUs potentially having different numbers of CPUs from each hemisphere.
Additionally, it is not feasible to ascertain the hemisphere based
solely on the CPU number.
Users wishing to assign their workload to all CPUs, or a subset of CPUs
within a specific hemisphere, encounter difficulties in identifying the
cpumask. To address this, it is proposed to expose hemisphere
information as a die in sysfs. This aligns with other architectures
and facilitates the identification of CPUs within the same hemisphere.
Tools such as lstopo can also access this information.
Please note: The hypervisor reveals the locality of the CPUs to
hemispheres only in dedicated mode. Consequently, in systems where
hemisphere information is unavailable, such as shared LPARs, the
die_cpus information in sysfs will mirror package_cpus, with
die_id set to -1.
Without this change.
$ grep . /sys/devices/system/cpu/cpu16/topology/{die*,package*} 2>/dev/null
/sys/devices/system/cpu/cpu16/topology/package_cpus:000000,000000ff,ffff0000
/sys/devices/system/cpu/cpu16/topology/package_cpus_list:16-39
With this change.
$ grep . /sys/devices/system/cpu/cpu16/topology/{die*,package*} 2>/dev/null
/sys/devices/system/cpu/cpu16/topology/die_cpus:000000,00000000,00ff0000
/sys/devices/system/cpu/cpu16/topology/die_cpus_list:16-23
/sys/devices/system/cpu/cpu16/topology/die_id:2
/sys/devices/system/cpu/cpu16/topology/package_cpus:000000,000000ff,ffff0000
/sys/devices/system/cpu/cpu16/topology/package_cpus_list:16-39
snipped lstopo-no-graphics o/p
Group0 L#0 (total=8747584KB)
Package L#0 (total=3564096KB CPUModel="POWER10 (architected), altivec supported" CPURevision="2.0 (pvr 0080 0200)")
NUMANode L#0 (P#0 local=3564096KB total=3564096KB)
Die L#0 (P#0)
Core L#0 (P#0)
<snipped>
Package L#1 (total=5183488KB CPUModel="POWER10 (architected), altivec supported" CPURevision="2.0 (pvr 0080 0200)")
NUMANode L#1 (P#1 local=5183488KB total=5183488KB)
Die L#2 (P#2)
Core L#2 (P#16)
L3Cache L#4 (size=4096KB linesize=128 ways=16)
L2Cache L#4 (size=1024KB linesize=128 ways=8)
L1dCache L#4 (size=32KB linesize=128 ways=8)
L1iCache L#4 (size=48KB linesize=128 ways=6)
PU L#16 (P#16)
PU L#17 (P#18)
PU L#18 (P#20)
PU L#19 (P#22)
L3Cache L#5 (size=4096KB linesize=128 ways=16)
L2Cache L#5 (size=1024KB linesize=128 ways=8)
L1dCache L#5 (size=32KB linesize=128 ways=8)
L1iCache L#5 (size=48KB linesize=128 ways=6)
PU L#20 (P#17)
PU L#21 (P#19)
PU L#22 (P#21)
PU L#23 (P#23)
Die L#3 (P#3)
Core L#3 (P#24)
L3Cache L#6 (size=4096KB linesize=128 ways=16)
L2Cache L#6 (size=1024KB linesize=128 ways=8)
L1dCache L#6 (size=32KB linesize=128 ways=8)
L1iCache L#6 (size=48KB linesize=128 ways=6)
PU L#24 (P#24)
PU L#25 (P#26)
PU L#26 (P#28)
PU L#27 (P#30)
L3Cache L#7 (size=4096KB linesize=128 ways=16)
L2Cache L#7 (size=1024KB linesize=128 ways=8)
L1dCache L#7 (size=32KB linesize=128 ways=8)
L1iCache L#7 (size=48KB linesize=128 ways=6)
PU L#28 (P#25)
PU L#29 (P#27)
PU L#30 (P#29)
PU L#31 (P#31)
Core L#4 (P#32)
L3Cache L#8 (size=4096KB linesize=128 ways=16)
L2Cache L#8 (size=1024KB linesize=128 ways=8)
L1dCache L#8 (size=32KB linesize=128 ways=8)
L1iCache L#8 (size=48KB linesize=128 ways=6)
PU L#32 (P#32)
PU L#33 (P#34)
PU L#34 (P#36)
PU L#35 (P#38)
L3Cache L#9 (size=4096KB linesize=128 ways=16)
L2Cache L#9 (size=1024KB linesize=128 ways=8)
L1dCache L#9 (size=32KB linesize=128 ways=8)
L1iCache L#9 (size=48KB linesize=128 ways=6)
PU L#36 (P#33)
PU L#37 (P#35)
PU L#38 (P#37)
PU L#39 (P#39)
Group0 L#1 (total=7736896KB)
Package L#2 (total=5170880KB CPUModel="POWER10 (architected), altivec supported" CPURevision="2.0 (pvr 0080 0200)")
NUMANode L#2 (P#2 local=5170880KB total=5170880KB)
Die L#4 (P#4)
<snipped>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20251112074859.814087-1-srikar@linux.ibm.com
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.