Viewing profile — pgaddict

I really wish they clearly documented the parameters used by each of the databases (or are we expected to dig those out of the .rs sources somehow?), and actual versions used (sayi…

Interesting paper. I only started reading / digesting it, but: - I'm not sure how to interpret the Figure 1. It says "Flash writes (KB) per page", but it doesn't really say which p…

So why does it happen only with hugepages? Is the extra overhead / TLB pressure enough to trigger the issue in some way? Of is it because the regular pages get swapped out (which h…

True. Unfortunately it's what index scans in Postgres do right now - it's the last "major" scan type not supporting some sort of prefetch (posix_fadvise or AIO). We're working on i…

To the best of my knowledge, yes. Unfortunately the details of how it was calculated in ~2000 seem to be lost, but the person who did that described he did it like this. It's possi…

Damn, I copied the wrong command. I wanted to copy this one: fio --filename=/dev/md127 --direct=1 --rw=randread --bs=8k --ioengine=io_uring --iodepth=1 --runtime=120 --numjobs=1 --…

Good idea. It's an interesting historical question - when we picked 4.0 as the default ~25 years ago, how close was is to the calculated value? I was asking that myself. Unfortunat…

Good point, I should have included that (the linked pgsql-hackers thread have some of this information, at least). I've observed exactly this behavior on a wide range of hardware /…

There probably is some additional inefficiency when reading pages randomly (compared to sequential reads), but most of the difference is at the storage level. That is, SSDs can han…

AFAIK these two joins are exactly the same once you get past the parsing. It's just a different way to write an inner join. It's translated into the same AST and so there's no diff…

That is part of the key idea, yes. It's more elaborate, because it can split the aggregate - it can do part of it before the join, and finalize it after the join. Similarly to what…

It's not about not knowing about an optimization. The challenge is to know when to apply it, so that it does not cause regressions for cases that can't benefit from it. It may be l…

IMHO the whole point of Qubes is that it does not do the compartmentalization at the level of individual applications, but groups of applications. Otherwise you'd need to very clea…

I'm not sure what exactly you mean by "thread" here. Postgres is not thread-based - there are people working on that, but for now it's all processes. Some of these limitations are …

I believe there are reasons why e.g. io_uring could be inherently slower in some cases, and I tried to point some of those out. With io_uring everything happens in the backend proc…

Debian 12/13, with kernel 6.15. Sorry, should have mentioned that in the blog post.

> Right now async IO is used for sequential scans and bitmap scans, not for index scans. My initial guess would be that it mostly helps for complex queries (that use multiple index…

I did a lot of tests comparing the io_method choices, and I'm yet to see a realistic query where it makes a significant difference of more than a couple percent (in either directio…

The funny thing is the local communist newspaper "Red Truth" (as if there were non-communist ones, ...) published a review of LOTR in 1977, in which they pretty much took the side …

The toaster mention reminded me of this: https://www.youtube.com/watch?v=LRq_SAuQDec This is how "talking to AI" feels like for anything mildly complex.

I've been involved in a couple of those cases, where a large company ran into an issue, and chose to solve it by migrating to something else. And while the issues certainly exist (…

I only noticed the jerky scrolling on pages with a lot of images, particularly hires + CSS effects (blur etc.). Everything else feels OK to me (I'm sure it could be smoother, but i…

Thanks for the clarification.

I occasionally see stutters too, even with Full HD video. Or more precisely, mplayer complained about slowness and having to drop frames. It often helped to actually give the VM mo…

Not sure what "mpv" means in this context, but this reminds me the one actual pet peeve I have with Qubes - video/audio calls just don't work for me. It either doesn't work or the …