[$] The 7.0 scheduler regression that wasn't
Date:
Fri, 17 Apr 2026 13:34:00 +0000
Description:
One of the more significant changes in the 7.0 kernel release is to use the lazy-preemption mode by default in the CPU
scheduler. The scheduler developers have wanted to reduce the number of preemption modes for years, and lazy preemption looks like a step toward
that goal. But then there came this report from Salvatore Dipietro that lazy preemption caused a 50% performance
regression on a PostgreSQL benchmark. Investigation showed that the
situation is not actually so grave, but the episode highlights just how sensitive some workloads can be to configuration changes; there may be surprises in store for other users as well.
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Link to news story:
https://lwn.net/Articles/1067029/
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