4e35b475a1
We used to always determine the number of CPU dies by counting unique values in `/sys/devices/system/cpu/cpu*/topology/die_id` files. This method works on x64 systems but is ineffective on ARM64. The `topology_die_id` function is defined for x64 architectures in `arch/x86/include/asm/topology.h` but is not implemented for ARM64 in `arch/arm64/include/asm/topology.h`. In Linux kernel 5.15 (used in Ubuntu 22.04), the `die_id` attribute is exposed with a value of -1 if `topology_die_id` is not defined for the architecture. Therefore, the `die_id` file for ARM64 consistently has the value -1, causing our method of counting unique values to always return 1 on Ubuntu 22.04, regardless of the actual number of dies. This can cause issues if number of sockets is more than 1, since our code assumes `total_dies` is a multiple of `total_sockets`. Starting with Linux kernel 5.17, a change was introduced [1] to expose the `die_id` file only if `topology_die_id` is defined for the architecture. Consequently, in Linux kernel 6.8 (used in Ubuntu 24.04), this file is absent for ARM64 systems. As a result, our method of counting unique values now produces 0 on Ubuntu 24.04. Given the lack of a straightforward way to determine the number of dies on ARM64 systems, this patch sets `total_dies` equal to `total_sockets`, assuming one die per socket. [1] https://github.com/torvalds/linux/commit/2c4dcd7
104 lines
2.9 KiB
Ruby
104 lines
2.9 KiB
Ruby
# frozen_string_literal: true
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require_relative "../model/spec_helper"
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RSpec.describe Prog::LearnCpu do
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subject(:lc) { described_class.new(Strand.new) }
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# Gin up a topologically complex processor to test summations.
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let(:eight_thread_four_core_four_numa_two_socket) do
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<<JSON
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{
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"cpus": [
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{
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"cpu": 0,
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"socket": 0,
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"core": 0
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},{
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"cpu": 1,
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"socket": 0,
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"core": 0
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},{
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"cpu": 2,
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"socket": 0,
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"core": 1
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},{
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"cpu": 3,
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"socket": 0,
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"core": 1
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},{
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"cpu": 4,
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"socket": 1,
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"core": 0
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},{
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"cpu": 5,
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"socket": 1,
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"core": 0
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},{
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"cpu": 6,
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"socket": 1,
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"core": 1
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},{
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"cpu": 7,
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"socket": 1,
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"core": 1
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}
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]
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}
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JSON
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end
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describe "#get_arch" do
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it "returns the architecture" do
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sshable = instance_double(Sshable)
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expect(sshable).to receive(:cmd).with("common/bin/arch").and_return("x64")
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allow(lc).to receive(:sshable).and_return(sshable)
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expect(lc.get_arch).to eq("x64")
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end
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it "fails when there's an unexpected architecture" do
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sshable = instance_double(Sshable)
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expect(sshable).to receive(:cmd).with("common/bin/arch").and_return("s390x")
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allow(lc).to receive(:sshable).and_return(sshable)
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expect { lc.get_arch }.to raise_error RuntimeError, "BUG: unexpected CPU architecture"
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end
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end
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describe "#get_topology" do
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it "returns the CPU topology" do
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sshable = instance_double(Sshable)
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expect(sshable).to receive(:cmd).with("/usr/bin/lscpu -Jye").and_return(
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eight_thread_four_core_four_numa_two_socket
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)
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allow(lc).to receive(:sshable).and_return(sshable)
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expect(lc.get_topology).to eq(Prog::LearnCpu::CpuTopology.new(total_cpus: 8, total_cores: 4, total_dies: 0, total_sockets: 2))
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end
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end
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describe "#count_dies" do
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it "returns the number of dies" do
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sshable = instance_double(Sshable)
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expect(sshable).to receive(:cmd).with("cat /sys/devices/system/cpu/cpu*/topology/die_id").and_return("0\n1\n0\n1\n")
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allow(lc).to receive(:sshable).and_return(sshable)
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expect(lc.count_dies(arch: "x64", total_sockets: 2)).to eq(2)
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end
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it "returns the number of sockets when on arm64" do
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sshable = instance_double(Sshable)
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allow(lc).to receive(:sshable).and_return(sshable)
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expect(lc.count_dies(arch: "arm64", total_sockets: 2)).to eq(2)
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end
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end
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describe "#start" do
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it "pops with cpu info" do
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allow(lc).to receive_messages(
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get_arch: "x64",
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get_topology: Prog::LearnCpu::CpuTopology.new(total_cpus: 8, total_cores: 4, total_dies: 0, total_sockets: 2),
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count_dies: 2
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)
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expect { lc.start }.to exit(arch: "x64", total_cpus: 8, total_cores: 4, total_dies: 2, total_sockets: 2)
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end
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end
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end
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