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| author |   Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2021-09-24 20:51:02 +1200 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2021-10-15 11:25:15 +0200 |
| commit | c5e22feffdd736cb02b98b0f5b375c8ebc858dd4 (patch) | |
| tree | a2b205953997c0dece4bf15261a4d1ac169be0ff /Documentation/ABI | |
| parent | sched: Disable -Wunused-but-set-variable (diff) | |
| download | linux-dev-c5e22feffdd736cb02b98b0f5b375c8ebc858dd4.tar.xz linux-dev-c5e22feffdd736cb02b98b0f5b375c8ebc858dd4.zip | |
topology: Represent clusters of CPUs within a die
Both ACPI and DT provide the ability to describe additional layers of
topology between that of individual cores and higher level constructs
such as the level at which the last level cache is shared.
In ACPI this can be represented in PPTT as a Processor Hierarchy
Node Structure [1] that is the parent of the CPU cores and in turn
has a parent Processor Hierarchy Nodes Structure representing
a higher level of topology.
For example Kunpeng 920 has 6 or 8 clusters in each NUMA node, and each
cluster has 4 cpus. All clusters share L3 cache data, but each cluster
has local L3 tag. On the other hand, each clusters will share some
internal system bus.
+-----------------------------------+ +---------+
| +------+ +------+ +--------------------------+ |
| | CPU0 | | cpu1 | | +-----------+ | |
| +------+ +------+ | | | | |
| +----+ L3 | | |
| +------+ +------+ cluster | | tag | | |
| | CPU2 | | CPU3 | | | | | |
| +------+ +------+ | +-----------+ | |
| | | |
+-----------------------------------+ | |
+-----------------------------------+ | |
| +------+ +------+ +--------------------------+ |
| | | | | | +-----------+ | |
| +------+ +------+ | | | | |
| | | L3 | | |
| +------+ +------+ +----+ tag | | |
| | | | | | | | | |
| +------+ +------+ | +-----------+ | |
| | | |
+-----------------------------------+ | L3 |
| data |
+-----------------------------------+ | |
| +------+ +------+ | +-----------+ | |
| | | | | | | | | |
| +------+ +------+ +----+ L3 | | |
| | | tag | | |
| +------+ +------+ | | | | |
| | | | | | +-----------+ | |
| +------+ +------+ +--------------------------+ |
+-----------------------------------| | |
+-----------------------------------| | |
| +------+ +------+ +--------------------------+ |
| | | | | | +-----------+ | |
| +------+ +------+ | | | | |
| +----+ L3 | | |
| +------+ +------+ | | tag | | |
| | | | | | | | | |
| +------+ +------+ | +-----------+ | |
| | | |
+-----------------------------------+ | |
+-----------------------------------+ | |
| +------+ +------+ +--------------------------+ |
| | | | | | +-----------+ | |
| +------+ +------+ | | | | |
| | | L3 | | |
| +------+ +------+ +---+ tag | | |
| | | | | | | | | |
| +------+ +------+ | +-----------+ | |
| | | |
+-----------------------------------+ | |
+-----------------------------------+ | |
| +------+ +------+ +--------------------------+ |
| | | | | | +-----------+ | |
| +------+ +------+ | | | | |
| | | L3 | | |
| +------+ +------+ +--+ tag | | |
| | | | | | | | | |
| +------+ +------+ | +-----------+ | |
| | +---------+
+-----------------------------------+
That means spreading tasks among clusters will bring more bandwidth
while packing tasks within one cluster will lead to smaller cache
synchronization latency. So both kernel and userspace will have
a chance to leverage this topology to deploy tasks accordingly to
achieve either smaller cache latency within one cluster or an even
distribution of load among clusters for higher throughput.
This patch exposes cluster topology to both kernel and userspace.
Libraried like hwloc will know cluster by cluster_cpus and related
sysfs attributes. PoC of HWLOC support at [2].
Note this patch only handle the ACPI case.
Special consideration is needed for SMT processors, where it is
necessary to move 2 levels up the hierarchy from the leaf nodes
(thus skipping the processor core level).
Note that arm64 / ACPI does not provide any means of identifying
a die level in the topology but that may be unrelate to the cluster
level.
[1] ACPI Specification 6.3 - section 5.2.29.1 processor hierarchy node
structure (Type 0)
[2] https://github.com/hisilicon/hwloc/tree/linux-cluster
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210924085104.44806-2-21cnbao@gmail.com
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/stable/sysfs-devices-system-cpu | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/ABI/stable/sysfs-devices-system-cpu b/Documentation/ABI/stable/sysfs-devices-system-cpu index 516dafea03eb..3965ce504484 100644 --- a/Documentation/ABI/stable/sysfs-devices-system-cpu +++ b/Documentation/ABI/stable/sysfs-devices-system-cpu @@ -42,6 +42,12 @@ Description: the CPU core ID of cpuX. Typically it is the hardware platform's architecture and platform dependent. Values: integer +What: /sys/devices/system/cpu/cpuX/topology/cluster_id +Description: the cluster ID of cpuX. Typically it is the hardware platform's + identifier (rather than the kernel's). The actual value is + architecture and platform dependent. +Values: integer + What: /sys/devices/system/cpu/cpuX/topology/book_id Description: the book ID of cpuX. Typically it is the hardware platform's identifier (rather than the kernel's). The actual value is @@ -85,6 +91,15 @@ Description: human-readable list of CPUs within the same die. The format is like 0-3, 8-11, 14,17. Values: decimal list. +What: /sys/devices/system/cpu/cpuX/topology/cluster_cpus +Description: internal kernel map of CPUs within the same cluster. +Values: hexadecimal bitmask. + +What: /sys/devices/system/cpu/cpuX/topology/cluster_cpus_list +Description: human-readable list of CPUs within the same cluster. + The format is like 0-3, 8-11, 14,17. +Values: decimal list. + What: /sys/devices/system/cpu/cpuX/topology/book_siblings Description: internal kernel map of cpuX's hardware threads within the same book_id. it's only used on s390. |