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use a prod-like shared_buffers size for some perf unit tests (#11373)

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## Problem

In Neon DBaaS we adjust the shared_buffers to the size of the compute,
or better described we adjust the max number of connections to the
compute size and we adjust the shared_buffers size to the number of max
connections according to about the following sizes
`2 CU: 225mb; 4 CU: 450mb; 8 CU: 900mb`

[see](877e33b428/goapp/controlplane/internal/pkg/compute/computespec/pg_settings.go (L405))

## Summary of changes

We should run perf unit tests with settings that is realistic for a
paying customer and select 8 CU as the reference for those tests.
This commit is contained in:
Peter Bendel
2025-04-02 12:43:05 +02:00
committed by GitHub
parent 7dc8370848
commit 4bc6dbdd5f
9 changed files with 43 additions and 7 deletions
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17
test_runner/fixtures/utils.py
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@@ -724,3 +724,20 @@ def skip_on_ci(reason: str):
os.getenv("CI", "false") == "true",
reason=reason,
)
def shared_buffers_for_max_cu(max_cu: float) -> str:
"""
Returns the string value of shared_buffers for the given max CU.
Use shared_buffers size like in production for max CU compute.
See https://github.com/neondatabase/cloud/blob/877e33b4289a471b8f0a35c84009846358f3e5a3/goapp/controlplane/internal/pkg/compute/computespec/pg_settings.go#L405
e.g. // 2 CU: 225mb; 4 CU: 450mb; 8 CU: 900mb
"""
ramBytes = int(4096 * max_cu * 1024 * 1024)
maxConnections = max(100, min(int(ramBytes / 9531392), 4000))
maxWorkerProcesses = 12 + int(max_cu * 2)
maxBackends = 1 + maxConnections + maxWorkerProcesses
sharedBuffersMb = int(max(128, (1023 + maxBackends * 256) / 1024))
sharedBuffers = int(sharedBuffersMb * 1024 / 8)
return str(sharedBuffers)