6f6267ce29
This commit introduces a hugepages configuration for postgres via a rhizome lib+bin. At the moment, it uses the default huge page size (2M), and calculates the number of huge pages as 25% of the total available memory. The setup adjusts the shared_buffers accordingly to fit the shared memory within the allocated number of hugepages. The configuration happens as an `ExecStartPre` script added to the existing systemd unit managed by pg_ctlcluster. To keep the semantics of the `start` command unchanged, the hugepages script *does not* stop an existing cluster to configure hugepages, and only does it when the cluster is not running. In a subsequent change, we can consider adding the boot parameters to setup 1G hugepages for larger instances (possibly standard-30+), where they are most useful. [1]: https://www.postgresql.org/docs/current/kernel-resources.html#LINUX-HUGE-PAGES
48 lines
2.0 KiB
Ruby
48 lines
2.0 KiB
Ruby
# frozen_string_literal: true
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require_relative "../lib/hugepages_setup"
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RSpec.describe HugepagesSetup do
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let(:logger) { instance_double(Logger, warn: nil) }
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let(:hugepages_setup) { described_class.new("17-main", logger) }
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describe "#setup_postgres_hugepages" do
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it "calculates hugepages via overhead subtraction and rounding" do
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# Mock hugepage info: 512 x 2MB hugepages = 1024MB total hugepage space
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expect(hugepages_setup).to receive(:hugepage_info).and_return([512, 2048])
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# shared_memory_size increases due to simulated overhead:
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# 1024MB -> 1061MB (37MB overhead)
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expect(hugepages_setup).to receive(:get_postgres_param)
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.with("shared_memory_size").and_return(1061)
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# Block size for rounding shared_buffers
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expect(hugepages_setup).to receive(:get_postgres_param)
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.with("block_size").and_return(8192) # 8KB blocks
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# First call: set shared_buffers to total hugepage space
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# (1024MB = 1,048,576 KiB)
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expect(hugepages_setup).to receive(:update_postgres_hugepages_conf)
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.with(1_048_576)
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# Second call: back off by overhead and round down to block boundary
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# overhead = (1061 - 1024) * 1024 = 37,888 KiB
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# target = 1,048,576 - 37,888 = 1,010,688 KiB
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expected_shared_buffers = 1_010_688
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expect(hugepages_setup).to receive(:update_postgres_hugepages_conf)
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.with(expected_shared_buffers)
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expect(expected_shared_buffers & 0b111).to eq(0) # Divisible by 8
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expect { hugepages_setup.setup_postgres_hugepages }.not_to raise_error
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end
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it "skips setup if no hugepages are configured" do
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expect(hugepages_setup).to receive(:hugepage_info).and_return([0, 2048])
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expect(hugepages_setup).not_to receive(:get_postgres_param)
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expect(hugepages_setup).not_to receive(:update_postgres_hugepages_conf)
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expect(logger).to receive(:warn).with("No hugepages configured, skipping setup.")
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expect { hugepages_setup.setup_postgres_hugepages }.not_to raise_error
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end
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end
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end
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