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MDEV-33070 Thread pool starvation at oversubscribe#4804

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gkodinov merged 1 commit intoMariaDB:10.11from
varundeepsaini:MDEV-33070-thread-pool-starvation
Mar 18, 2026
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MDEV-33070 Thread pool starvation at oversubscribe#4804
gkodinov merged 1 commit intoMariaDB:10.11from
varundeepsaini:MDEV-33070-thread-pool-starvation

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@varundeepsaini varundeepsaini commented Mar 14, 2026 •
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Summary

  • allow a thread group to reach the oversubscribe threshold before treating it as oversubscribed
  • add an MTR regression test for MDEV-33070 covering queued work at the threshold

Testing

  • Added a regression test

@gkodinov gkodinov added the External Contribution All PRs from entities outside of MariaDB Foundation, Corporation, Codership agreements. label Mar 16, 2026
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Thank you for your contribution! This is a preliminary review.

vaintroub
vaintroub reviewed Mar 16, 2026
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Commented on test case. The one-liner code fix is ok, but test needs some improvement (and explanation)

@varundeepsaini varundeepsaini force-pushed the MDEV-33070-thread-pool-starvation branch 4 times, most recently from 3b1f419 to dfd6a1d Compare March 18, 2026 06:07
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Thank you! Looks quite good to me, nice explanation for the test case.
The only thing that I'd remove is a synchronous SELECT SLEEP(1), as commented. Perhaps you can slightly increase wait_timeout up from 2 seconds, when checking that INSERT went through(as commented, CI sometimes have weird timing issues), though I do not have a very strong opinion.

@varundeepsaini varundeepsaini force-pushed the MDEV-33070-thread-pool-starvation branch from dfd6a1d to 7af1a72 Compare March 18, 2026 10:24
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Thanks for addressing my comments! Looks good to me now.

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LGTM. Thanks for working on this.

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Please rebase to 10.11: this is a bug fix and it needs to be in the lowest affected version.

@gkodinov gkodinov changed the base branch from main to 10.11 March 18, 2026 11:42
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gkodinov commented Mar 18, 2026

I will rebase. and merge.

@gkodinov gkodinov force-pushed the MDEV-33070-thread-pool-starvation branch from 7af1a72 to aea0a9f Compare March 18, 2026 11:57
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rebased.

@varundeepsaini @gkodinov
MDEV-33070 Thread pool starvation at oversubscribe
3735d28 
Allow one more worker at the oversubscribe threshold so a group
only becomes oversubscribed after it exceeds the configured
limit.

Add a regression test that reproduces the starvation case in the
generic thread pool and verifies queued work still drains.

Signed-off-by: Varun Deep Saini <varun.23bcs10048@ms.sst.scaler.com>
@gkodinov gkodinov force-pushed the MDEV-33070-thread-pool-starvation branch from aea0a9f to 3735d28 Compare March 18, 2026 11:58
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varundeepsaini commented Mar 18, 2026

@gkodinov Thanks a lot !! ❤️

@gkodinov gkodinov merged commit ad5ef77 into MariaDB:10.11 Mar 18, 2026
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