An AWS engineer discovered that the Linux 7.0 development kernel cuts PostgreSQL throughput roughly in half on Graviton4 hardware. The regression was traced to Linux 7.0 restricting available kernel preemption modes, causing significantly more time spent in user-space spinlocks. A patch was proposed to restore PREEMPT_NONE as the default, but kernel maintainer Peter Zijlstra pushed back, arguing the proper fix is for PostgreSQL to adopt the Restartable Sequences (RSEQ) time slice extension introduced in Linux 7.0. If the patch is rejected, PostgreSQL users could face major performance degradation when Linux 7.0 stable ships in approximately two weeks.
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