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AWS engineer reports PostgreSQL perf halved by Linux 7.0, fix may not be easy

AWS engineer reports PostgreSQL perf halved by Linux 7.0, fix may not be easy

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Comments (53)

  • lfittl
    Its worth reading this follow-up LKML post by Andres Freund (who works on Postgres): https://lore.kernel.org/lkml/yr3inlzesdb45n6i6lpbimwr7b25kqk...
  • dsr_
    Nobody sensible runs the latest kernel; nobody running PG in production should be afraid of setting a non-default at either boot time or as a sysctl. So this will, most likely, be another step in building a PG database server (turn off pre-emption if your kernel is 7.0 or later and PG is pre-whatever-version).At worst it might become a permanent part of building a PG server and a FAQ... but if it affects one thing this badly, it will affect others.
  • longislandguido
    Anyone check to see if Jia Tan has submitted any kernel patches lately?
  • harshreality
    Background on PREEMPT_LAZY:https://lwn.net/Articles/994322/
  • monocasa
    I feel like using spinlocks in user space at all without kernel support like rseq is just asking for weird performance degradations.
  • cperciva
    This makes me feel better about the 10% performance regression I just measured between FreeBSD 14 and FreeBSD 15.0.
  • up2isomorphism
    Not sure why people have to upgrade to the newest major kernel version as soon as it is released.
  • anal_reactor
    Can someone explain to me what's the problem? I have very little knowledge of Linux kernel, but I'm curious. I've tried reading a little, but it's jargon over jargon.
  • galbar
    It's not a good look to break userspace applications without a deprecation period where both old and new solutions exist, allowing for a transition period.
  • FireBeyond
    Once upon a time, Linus would shout and yell about how the kernel should never "break" userspace (and I see in some places, some arguments of "It's not broken, it's just a performance regression" - personally I'd argue a 50% hit to performance of a pre-eminent database engine is ... quite the regression).Now, the kernel engineer who introduced the brand new mechanism (introduced in Linux 7.0) for handling pre-emption says the "fix" is for Postgres to start using this new mechanism (I think the sister comment below links to what one of the Postgres engineers thinks of that, and I'm inclined mostly to agree).
  • cdelsolar
  • anon
    undefined