[CDRIVER-4300] Lock contention in mongoc_ts_pool_return Created: 17/Feb/22  Updated: 21/Nov/23  Resolved: 21/Nov/23

Status: Closed
Project: C Driver
Component/s: Performance
Affects Version/s: None
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: Raiden Worley (Inactive) Assignee: Kyle Kloberdanz
Resolution: Gone away Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Quarter: FY24Q3

 Description   

Following up on the improvements in CDRIVER-4002 as part of PERF-2203, we are still seeing some lesser contention in mongoc_ts_pool_return. We are seeing between 38 and 136 samples out of 2500 samples waiting on this lock.

This is far better than before the upgrade with CDRIVER-4002, but may be responsible for part of the 14 ms latency we're seeing.

Please loop me in to any investigations here; now that TIG-3599 has been done we can revendor the C++ driver into genny very quickly and easily, so can very tightly iterate with y'all on this.



 Comments   
Comment by Kyle Kloberdanz [ 21/Nov/23 ]

After extensive testing, I was unable to replicate this issue. Because PERF-2203 is already over a year and a half old as of writing, all people associated with this ticket are no longer with the company, and none of the current members of the perf or Genny teams have encountered this issue, we have decided to close this ticket as "Gone Away". If anyone encounters this issue, please re-open it and notify the C Driver team. Please share any and all steps necessary to recreate the issue.

I detailed how to recreate my testing in Confluence here:

https://wiki.corp.mongodb.com/display/DRIVERS/Lock+Contention+Issue+In+The+Mongo+C+Driver

Comment by Raiden Worley (Inactive) [ 24/Feb/22 ]

We are also seeing a lot of samples in mc_tpld_modify_begin, see comments on the related perf ticket. Posting in this ticket in case they're related, but can spin out a separate ticket if preferred.

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