[SERVER-66149] Investigate write stalls in mixed_workloads with dynamic concurrency Created: 03/May/22  Updated: 12/May/22  Resolved: 12/May/22

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Major - P3
Reporter: Daniel Gomez Ferro Assignee: Daniel Gomez Ferro
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: PNG File image-2022-05-03-16-53-28-828.png    
Issue Links:
Related
Sprint: Execution Team 2022-05-16
Participants:

 Description   

When running with few read/write tickets, the mixed_workloads_genny test has episodes where writes are stopped and only reads get through:



 Comments   
Comment by Daniel Gomez Ferro [ 12/May/22 ]

In this workload, after a long running checkpoint we accumulate lots of updates in the `config.transactions` collection (each write updates its session document). When the checkpoint transaction finishes all those updates become obsolete and WT decides to evict the page to trim the long update chain. This will happen for most pages in the collection, so write throughput gets severely affected during this time. If we had more write tickets the effect might not be as noticeable because we'd evict much more pages in parallel.

The cause for the long running checkpoint could be high CPU utilization.

Generated at Thu Feb 08 06:04:38 UTC 2024 using Jira 9.7.1#970001-sha1:2222b88b221c4928ef0de3161136cc90c8356a66.