[improvement](executor) use real elapsed time to compute workload group metrics refresh interval#63244
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bosswnx wants to merge 2 commits into
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[improvement](executor) use real elapsed time to compute workload group metrics refresh interval#63244bosswnx wants to merge 2 commits into
bosswnx wants to merge 2 commits into
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…up metrics refresh interval Replace the fixed config-based interval with the actual monotonic time delta between two refreshes when calculating per-second CPU and scan IO rates in WorkloadGroupMetrics, so the rates stay accurate even when the refresh thread is delayed or the configured interval is changed at runtime.
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Thank you for your contribution to Apache Doris. Please clearly describe your PR:
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run buildall |
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TPC-H: Total hot run time: 29661 ms |
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TPC-DS: Total hot run time: 169745 ms |
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run buildall |
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TPC-H: Total hot run time: 29528 ms |
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TPC-DS: Total hot run time: 171560 ms |
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BE UT Coverage ReportIncrement line coverage Increment coverage report
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BE UT Coverage ReportIncrement line coverage Increment coverage report
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BE Regression && UT Coverage ReportIncrement line coverage Increment coverage report
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What problem does this PR solve?
Issue Number: N/A
Related PR: N/A
Problem Summary:
WorkloadGroupMetrics::refresh_metrics()computes per-second CPU time andlocal/remote scan bytes by dividing the delta of each counter by an interval
derived from
config::workload_group_metrics_interval_ms:This is inaccurate for several reasons:
workload_group_metrics_interval_ms. Under BE load or scheduling delaysthe actual gap between two refreshes can drift significantly, but the
divisor is still the configured interval, so the reported per-second
rates do not reflect reality.
workload_group_metrics_interval_msis changed at runtime, thedivisor updates immediately while the counter delta still spans the
old interval, producing a one-shot incorrect rate.
workload_group_metrics_interval_ms < 1000, the integer divisionrounds the divisor down to
0, which would cause a divide-by-zero.This PR replaces the fixed config-based interval with the actual
monotonic time delta between two consecutive
refresh_metrics()invocations:
A new member
std::atomic<uint64_t> _last_refresh_time_ms{0}is added torecord the timestamp of the previous refresh. This makes the per-second
CPU / local-scan / remote-scan metrics reflect the true elapsed wall-clock
interval, regardless of refresh-thread jitter or runtime config changes.
Known limitation: on the very first invocation after BE startup
_last_refresh_time_msis0, sointerval_secondbecomesMonotonicMillis() / 1000(a large number) and the first sample of eachper-second metric will be reported as near-zero. The values converge to
correct readings from the second refresh onwards. A follow-up may
initialize
_last_refresh_time_mstoMonotonicMillis()in theconstructor; kept out of this PR to keep the change minimal.
Release note
None
Check List (For Author)
Test
the per-second-rate divisor with a more accurate value; the
metric semantics, plumbing and existing workload-group metrics
tests remain unchanged.
Behavior changed:
Does this need documentation?