Viewing profile — anarazel

Small addendum: Unless the whole table is in that state (or even newer), vacuum shouldn't do a full table scan, but only process not yet vacuumed parts of the table. There are some…

> Well also I know Postgres UNIQUE indexes provide additional locking. Like you can do an INSERT... WHERE NOT EXISTS or INSERT... ON CONFLICT that is guaranteed to succeed. That's …

Indeed. Not enough coffee, apparently.

There's a bunch of nastiness around that too. If you have e.g. library state that assumes the fd still works you can get her very confusing bugs once another file is opened into th…

It is somewhat interesting that the most widely used "big" OS that doesn't use fork, i.e. Windows, has dog slow process creation... I agree that there should be non-fork primitives…

> Use of the "h" register slices (bits 8..15) by compilers is thankfully pretty rare -- otherwise this would have been noticed much sooner! It's actually pretty easy to get compile…

> It's not the default (read committed is) and I never saw serializable being set in actual production systems. It's not the common mode of deployment, but it's definitely in prod …

The GOT has to be initially writable regardless of ifunc, even with relro, to apply relocations.

> It is a crime that postgres isn't able to allocate with 1GB huge pages by changing a config parameter in 2026 It is able to? Configure huge_page_size=1GB? Support for 2MB pages w…

I stopped drinking a few years back, after some (unrelated) health stuff. I don't miss wine, beer, that stopped - like for the author - after a relatively short amount of time. But…

Ability to trivially use custom VM images was quite nice. The amount of CI time spent installing dependencies or copying a cache of installed stuff is nontrivial. Particularly for …

Weirdly enough, I loved coffee from the first time I tried it, at maybe 13. Even though, looking back, it must have been terrible coffee, it was at something vaguely model UN like …

> ... so that leaves me confused. My understanding is that the regression is triggered with the 7.0+ kernel and can be mitigated with huge pages turned on. It gets a bit worse with…

The contention does exist in older kernels and is quite substantial.

> That 64-bit atomic in the buffer head with flags, a spinlock, and refcounts all jammed into it is nasty. Turns out to be pretty crucial for performance though... Not manipulating…

> > On x86 a spinlock release doesn't need a memory barrier (unless you do insane things) / lock prefix, but a futex based lock does (because you otherwise may not realize you need…

Addendum big enough to warrant a separate post: The fact the contention is a spinlock, rather than a futex is unrelated to the "regression". A quick hack shows the contended perfor…

I really dislike the use of spinlocks in postgres (and have been replacing a lot of uses over time), but it's not always easy to replace them from a performance angle. On x86 a spi…

I don't fully know, but I suspect it's just that due to the minor faults and tlb misses there is terrible contention with the spinlock, regardless of the PREEMPT_LAZY when using 4k…

Yes, I did reproduce it (to a much smaller degree, but it's just a 48c/96t machine). But it's an absurd workload in an insane configuration. Not using huge pages hurts way more tha…

Cross building of possible, but it's rather useful to be able to test the software you just built... And often enough, tests take more resources than the build.

Just German, not European, but still a start: https://en.wikipedia.org/wiki/Sovereign_Tech_Agency

It's very heavily dependent on what your processes are doing. I've seen extreme cases where the gains of pinning were large (well over 2x when cooperative tasks were pinned to the …

> PostgreSQL shares other caches between processes so they probably could have a global plan cache if they wanted. I wonder why they don’t though. > One possible reason is that the…

I would hope it's at least 3-4 orders of magnitude slower than a "traditional QR library". It'd be quite the indictment for such libraries, if not.