April 4, 2026
Half-speed Postgres, full-speed drama
AWS Engineer Reports PostgreSQL Perf Halved by Linux 7.0, Fix May Not Be Easy
Kernel change halves Postgres speed; devs bicker over who fixes it
TLDR: Linux 7.0 reportedly cuts PostgreSQL performance by about 50%, and kernel devs suggest the database should adopt a new feature instead of reverting changes. Comments are a brawl between “don’t break userspace,” “just tune it,” and jokes that Ubuntu’s next LTS means Long-Term Slowdown.
AWS rang the alarm: on Linux 7.0, PostgreSQL—a super-popular database—suddenly runs at about half speed on Amazon’s Graviton4 chips. Cue the internet pile-on. The twist? Kernel folks say the “fix” isn’t rolling back the change, but for Postgres to adopt a new trick called Restartable Sequences (RSEQ). That’s where the drama explodes: is Linux breaking userspace, or should Postgres adapt?
Commenters are split into camps. The purists channel the old Linus line—“don’t break userspace”—with one highlight calling a 50% hit “quite the regression.” Pragmatists shrug: nobody sane deploys the freshest kernel in production, just flip a setting or ship a tuned build. Meanwhile, standards-sticklers fume it’s “not a good look” to force app changes without a transition period. Some linked deep dives like Andres Freund’s detailed follow-up on the kernel list (read it here) and background on PREEMPT_LAZY (LWN explainer).
With Linux 7.0 due in two weeks—and powering Ubuntu 26.04 LTS—memes rolled in: “LTS = Long-Term Slowdown,” and “postgreSLOW.” The core fight is simple, even if the tech isn’t: who changes course? Kernel devs or the database team? Until someone blinks, users fear real-world slowdowns and emergency tuning guides.
Key Points
- •An AWS engineer measured PostgreSQL throughput at ~0.51x on Linux 7.0 versus prior kernels on a Graviton4 server, with higher user-space spinlock time.
- •The regression was traced to Linux 7.0’s restriction of kernel preemption modes introduced with scheduler updates.
- •A patch was posted to restore PREEMPT_NONE as the default preemption model to address the regression.
- •Kernel developer Peter Zijlstra indicated the fix should be for PostgreSQL to adopt the RSEQ time slice extension, which is supported in Linux 7.0.
- •Linux 7.0 stable is expected in about two weeks and is slated to power Ubuntu 26.04 LTS later in April.