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diff --git a/Documentation/powerpc/associativity.rst b/Documentation/powerpc/associativity.rst deleted file mode 100644 index 4d01c73685..0000000000 --- a/Documentation/powerpc/associativity.rst +++ /dev/null @@ -1,105 +0,0 @@ -============================ -NUMA resource associativity -============================ - -Associativity represents the groupings of the various platform resources into -domains of substantially similar mean performance relative to resources outside -of that domain. Resources subsets of a given domain that exhibit better -performance relative to each other than relative to other resources subsets -are represented as being members of a sub-grouping domain. This performance -characteristic is presented in terms of NUMA node distance within the Linux kernel. -From the platform view, these groups are also referred to as domains. - -PAPR interface currently supports different ways of communicating these resource -grouping details to the OS. These are referred to as Form 0, Form 1 and Form2 -associativity grouping. Form 0 is the oldest format and is now considered deprecated. - -Hypervisor indicates the type/form of associativity used via "ibm,architecture-vec-5 property". -Bit 0 of byte 5 in the "ibm,architecture-vec-5" property indicates usage of Form 0 or Form 1. -A value of 1 indicates the usage of Form 1 associativity. For Form 2 associativity -bit 2 of byte 5 in the "ibm,architecture-vec-5" property is used. - -Form 0 ------- -Form 0 associativity supports only two NUMA distances (LOCAL and REMOTE). - -Form 1 ------- -With Form 1 a combination of ibm,associativity-reference-points, and ibm,associativity -device tree properties are used to determine the NUMA distance between resource groups/domains. - -The “ibm,associativity” property contains a list of one or more numbers (domainID) -representing the resource’s platform grouping domains. - -The “ibm,associativity-reference-points” property contains a list of one or more numbers -(domainID index) that represents the 1 based ordinal in the associativity lists. -The list of domainID indexes represents an increasing hierarchy of resource grouping. - -ex: -{ primary domainID index, secondary domainID index, tertiary domainID index.. } - -Linux kernel uses the domainID at the primary domainID index as the NUMA node id. -Linux kernel computes NUMA distance between two domains by recursively comparing -if they belong to the same higher-level domains. For mismatch at every higher -level of the resource group, the kernel doubles the NUMA distance between the -comparing domains. - -Form 2 -------- -Form 2 associativity format adds separate device tree properties representing NUMA node distance -thereby making the node distance computation flexible. Form 2 also allows flexible primary -domain numbering. With numa distance computation now detached from the index value in -"ibm,associativity-reference-points" property, Form 2 allows a large number of primary domain -ids at the same domainID index representing resource groups of different performance/latency -characteristics. - -Hypervisor indicates the usage of FORM2 associativity using bit 2 of byte 5 in the -"ibm,architecture-vec-5" property. - -"ibm,numa-lookup-index-table" property contains a list of one or more numbers representing -the domainIDs present in the system. The offset of the domainID in this property is -used as an index while computing numa distance information via "ibm,numa-distance-table". - -prop-encoded-array: The number N of the domainIDs encoded as with encode-int, followed by -N domainID encoded as with encode-int - -For ex: -"ibm,numa-lookup-index-table" = {4, 0, 8, 250, 252}. The offset of domainID 8 (2) is used when -computing the distance of domain 8 from other domains present in the system. For the rest of -this document, this offset will be referred to as domain distance offset. - -"ibm,numa-distance-table" property contains a list of one or more numbers representing the NUMA -distance between resource groups/domains present in the system. - -prop-encoded-array: The number N of the distance values encoded as with encode-int, followed by -N distance values encoded as with encode-bytes. The max distance value we could encode is 255. -The number N must be equal to the square of m where m is the number of domainIDs in the -numa-lookup-index-table. - -For ex: -ibm,numa-lookup-index-table = <3 0 8 40>; -ibm,numa-distace-table = <9>, /bits/ 8 < 10 20 80 20 10 160 80 160 10>; - -:: - - | 0 8 40 - --|------------ - | - 0 | 10 20 80 - | - 8 | 20 10 160 - | - 40| 80 160 10 - -A possible "ibm,associativity" property for resources in node 0, 8 and 40 - -{ 3, 6, 7, 0 } -{ 3, 6, 9, 8 } -{ 3, 6, 7, 40} - -With "ibm,associativity-reference-points" { 0x3 } - -"ibm,lookup-index-table" helps in having a compact representation of distance matrix. -Since domainID can be sparse, the matrix of distances can also be effectively sparse. -With "ibm,lookup-index-table" we can achieve a compact representation of -distance information. |