Does it actually work?

Posted Apr 10, 2025 13:32 UTC (Thu) by khim (subscriber, #9252)
In reply to: Does it actually work? by Wol
Parent article: Three ways to rework the swap subsystem

> Do MacOs and Windows use paging?

Windows and MacOS have essentially the same API as Linux. MacOS is POSIX and Windows can run Linux binaries (WSL1, WSL2 runs full Linux kernel).

So no, that's not it.

I'm pretty sure they both include tons of tweaks and hacks to ensure that even if system is heavily trashing it still stays responsive, but the end result: if system is heavily overloaded it, definitely, becomes “sluggish”, but noting like Linux does where switch from graphic to text console may take hours (literally) and then you couldn't log in on text console because of timeouts (measured in minutes).

And if keeping system usable when it's swapping is explicit non-goal then I wonder why does anyone care to benchmark things that are not supposed to be used, anyway.

As I have said: I always assumed that Linux just simply keeps swap in some vestigial form for a nostalgia reasons (and no one cares to do anything to it) – and this is done to keep it working great in a “normal” situation (when swap is not used).

This even may be a sane stance if you recall that most Linux system don't really use swap (but Android and ChromeOS use swap code to implement zram… would explain these additions to that code that article discusses).

But when I read about some regressions and other such things… hey, that means that someone, somewhere still uses swap on Linux, for something.

The whole system have looked ever more mysterious the more I read an article: because it certainly read as if it comes from some parallel universe where something else but “zero swap but some zram” is used…

But… how and why? Why do they care about speed… and what kind of speed they do care about? Because for me swap on Linux always had one and one speed only: unusable. Was that it's 10x of “unusable” threshold or 100x of “unusable” threshold… I don't know: one thinks that should happen in seconds start taking hours system is no longer usable and measuring “speed of swap” doesn't make much sense, after that point.

Of course for me “speed of swap” is “slowdown compared to the situation when there are enough memory and swap is not used” and, maybe, there are some other ways to measure speed of swap, but… again: who, how and why does that?

That meta-mystery remained uncovered in the article…