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Type: Task
Resolution: Unresolved
Priority: Major - P3
Fix Version/s: None
Affects Version/s: None
Component/s: DHandles
Labels:
None

Assigned Teams:

Storage Engines - Foundations
Total Hours with Assigned Team:
380.787
Epic Link:
Disagg Bugs
Sprint:
SE Foundations - 2026-06-23
Story Points:
8

Background

SLS-6071 reports that Disaggregated Storage (DSC) exhibits a regression of over 60% in OperationThroughput compared to classic MongoDB (ASC) on the data_handle_locust workload. Latency is also significantly higher on DSC. This was initially surfaced in PERF-7206.

Observed Numbers

Test Name	Measurement	ASC (Classic)	DSC	DS vs ASC (%)
CreateOne	Latency50thPercentile	12.782	29.2512	+128.85%
CreateOne	Latency95thPercentile	36.155	334.2754	+824.56%
CreateOne	OperationThroughput	18.19	6.72	-63.03%
FindOne	Latency50thPercentile	0.432	0.5132	+18.80%
FindOne	Latency95thPercentile	0.867	1.309	+50.98%
FindOne	OperationThroughput	13894.99	5187.71	-62.66%
UpdateOne	Latency50thPercentile	12.025	29.2082	+142.90%
UpdateOne	Latency95thPercentile	34.331	331.642	+865.91%
UpdateOne	OperationThroughput	19.47	6.70	-65.50%

Goal

Investigate the root cause of the DSC performance gap on the high-active-dhandle workload and identify potential improvements. Per the comment in SLS-6071, the regression may be related to DSC's use of layered tables.

Suggested Investigation Areas

Profile DSC under the data_handle_locust workload to identify hot paths vs ASC
Examine data handle open/close/sweep costs in DSC (layered table overhead vs standard btree)
Check whether dhandle cache eviction or sweep behaviour differs significantly between ASC and DSC
Review lock contention on the dhandle list in the DSC layered-table code path
Compare checkpoint and reconciliation costs between ASC and DSC under this workload
Assess whether the 95th-percentile latency spikes (8-9x on write operations) point to periodic stalls (e.g. flush/ingest)