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Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

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Re: Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

#4

Post by baq »

TLDR of the LMKL thread: 120GB RAM postgres with hugepages=off, lock contention went from terrible to abysmal. nothing to see here except that amazon for whatever reason runs DB tests with huge pages disabled. (hope I'm not paying for RDS and auroras like that in production!)

Re: Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

#6

Post by nobleach »

PunchyHamster wrote: post #3

Seems Linus needs to yell at someone again. Especially with containers around you might very well hit the case of running new kernel but older version of PostgreSQL with no code mitigation for the problem

I get that folks love a good Linus rant. But as someone who's been at the end of that style of "feedback", nothing can be more humiliating or demotivating. Certainly there are contributors that are making "rookie mistakes". There are folks that aren't willing to ingest the entire context of what was tried back in 2.0.36, 2.2, 2.4... etc. And perhaps it's wise to simply stay away until you're completely certain you've got the chops to contribute. More than half the folks that enjoy that sort of abuse don't have those chops.

I can defend someone who is unwilling to yield on quality. Afterall, this truly is his baby. Issuing scathing rebukes to well-intentioned contributors is like slapping my kid when he brings me the wrong type of screwdriver.

Re: Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

#7

Post by Twirrim »

baq wrote: post #4

TLDR of the LMKL thread: 120GB RAM postgres with hugepages=off, lock contention went from terrible to abysmal. nothing to see here except that amazon for whatever reason runs DB tests with huge pages disabled. (hope I'm not paying for RDS and auroras like that in production!)

Huge pages has had a spotty history, that lead to people being paranoid about it, and no doubt a whole bunch of folks just disable it "because that's what we've always done". It has been stable and reliable for quite a while now, would really hope folks could move away from that perspective.

Re: Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

#8

Post by nijave »

Twirrim wrote: post #7
baq wrote: post #4

TLDR of the LMKL thread: 120GB RAM postgres with hugepages=off, lock contention went from terrible to abysmal. nothing to see here except that amazon for whatever reason runs DB tests with huge pages disabled. (hope I'm not paying for RDS and auroras like that in production!)

Huge pages has had a spotty history, that lead to people being paranoid about it, and no doubt a whole bunch of folks just disable it "because that's what we've always done". It has been stable and reliable for quite a while now, would really hope folks could move away from that perspective.

I tested it once about 2 years ago on Azure VM and got a nice 10-15% perf boost on pgbench (I want to say at least 64GB shared mem)

Re: Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained

#9

Post by mplanchard »

baq wrote: post #4

TLDR of the LMKL thread: 120GB RAM postgres with hugepages=off, lock contention went from terrible to abysmal. nothing to see here except that amazon for whatever reason runs DB tests with huge pages disabled. (hope I'm not paying for RDS and auroras like that in production!)

Also was only on ARM, wasn’t it?
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