FreeBSD ate my RAM

https://crocidb.com/post/freebsd-ate-my-ram/

198 70 19 days ago

jmclnx• 19 days ago

Interesting post, it made me wonder. At one time FreeBSD swap usage/logic was far better than what Linux did. Is that still the case ?

shevy-java• 19 days ago

I remember how NetBSD promoted itself as running on many more toasters than Linux once.

Then some NetBSD dev wrote on their mailing list that this is no longer true. Linux runs on more toasters now. (And also top 500 supercomputers, but toasters are the real metal to the petal test.)

These fights always remind me of:

https://www.jwz.org/doc/worse-is-better.html

It's an interesting piece of history too. I kind of evaluate it a bit differently, e. g. my summary is "momentum beats academic perfection". Which is not completely what it is about, but it is my own imperfect TL;DR summary.

bee_rider• 19 days ago

This basically fits my stereotype of BSD being a little bit more hardcore while Linux is a little more accessible… when the question was “can you install an OS on a toaster,” BSD had an advantage. Now that normal engineers have to make IOT toasters (for some reason) Linux should have the advantage, right?

Levitating• 19 days ago

why did that url point me to a scrotum in an egg cup

Someone• 19 days ago

but toasters are the real metal to the petal test.

Or is that a new tongue in cheek idiom?

AFAIK, it’s peDal, not peTal, and the other way around: pedal to the metal. The literal meaning is to push your accelerator pedal down to the floor of your car, which is made of metal.

0x4572• 19 days ago

Yes, It's just not every tool is aware of ZFS ARC. Which is what this post is about. Author just describes in an odd way.

mike_hock• 18 days ago

It's a bit odd that you have to query a filesystem-specific value to get simple memory usage stats.

man8alexd5• 19 days ago

FreeBSD didn’t have memory overcommit and instead used strict swap reservation - each allocated anonymous memory page was supposed to have a corresponding swap page. This required 2x RAM swap space, otherwise you would get “out of swap” when forking a large process. FreeBSD implemented memory overcommit around 2000.

jandrese• 19 days ago

Oh, so that's where that old nugget of wisdom came from! I've heard the rule about making your swap at least 2x your RAM for ages and thought it was just some old rule of thumb from the 80s. I didn't know there used to be a legitimate reason for it.

m463• 19 days ago

the end struck me - a picture of an os book. I wonder if students these days retain their books after college, or do they get returned as a rental?

linguae• 19 days ago

I'm a professor at a community college in Silicon Valley, and my students use online textbooks. I try to use Creative Commons or other libre textbooks, but sometimes I use paid textbooks when they are heads-and-shoulders better than their libre alternatives. Some e-textbooks can be accessed on a subscription basis. I admit I prefer non-subscription materials, but a colleague advised me that often the book that students learn from is different from a good reference book that students can use once they've already learned the material. For example, my colleagues and I have had great success with an online, interactive textbook for discrete math. While the subscription is unfortunately only valid for the duration of the course, once students have learned discrete math, they could buy a used copy of Rosen's discrete math textbook as a reference.

The nice thing about e-textbooks is not needing to carry around a bunch of heavy books. I remember the tomes I had in my college days, such as Stewart's Calculus.

NooneAtAll32• 19 days ago

just hint students towards anna's archive and then sky's the limit

saghm4• 18 days ago

The nice thing about e-textbooks is not needing to carry around a bunch of heavy books. I remember the tomes I had in my college days, such as Stewart's Calculus.

I'm not sure how relatable this is for people outside of my age group (late millennial), but growing up we used to get chided about stuffing too much in our backpacks and shown presentations about how we were going to give ourselves scoliosis, but then had like two minutes between classes that might be on the other side of the building (meaning no time to stop at our lockers other than at lunch) and we'd get chided even worse if we didn't have our textbooks available for the days we happened to need them in class (which of course we were never told in advance, and some classes had multiple textbooks that wouldn't all get used every time).

I wish that we had iPads or Chromebooks or whatever back when I was in school not even because I would have wanted to have been able to surf the web or play games or whatever, but just to have a solution to having to pick between having a sore back or getting worse scolding (with a side course of hypocrisy either way).

post-it• 19 days ago

I bought as few textbooks as I could, but the few that I did buy are sitting in my parents' basement bookshelves somewhere.

saghm4• 19 days ago

I graduated a decade ago but there was a pretty decent post-semester market for people selling their textbooks to other students (mostly via posting in various Facebook groups). Given the cost of college nowadays, if that ends up saving students a bit of money, it's probably worth it over saving the textbooks themselves.

Most years my parents ended up just driving my stuff to my aunt's house where she kept it in her garage over the summer after I packed it all up since I grew up several states away but my aunt loved in the area, and by the end of senior year, the textbooks I never managed to sell had added up to almost an entire extra bin (which was heavier than any of the others because they mostly just had clothes). For people who didn't have parents who loved driving everywhere in a large enough car or relatives in the area, this seems like it would be even more annoying (potentially ending up with just donating the leftover textbooks or maybe leaving them on the street like furniture and stuff often is at the end of the year on campuses). If people want to keep their textbooks, more power to them, but I'm not convinced that having a cheaper way that also simplifies the logistics of moving isn't better.

kogasa240p• 18 days ago

In college ATM and while I usually keep old textbooks, I have sold a couple on ebay to free up shelf space.

duendefm• 19 days ago

Thank you for such a quality post.

tiffanyh2• 19 days ago

If you like this kind of post, you might like this “htop explained” post.

https://peteris.rocks/blog/htop/

NooneAtAll32• 19 days ago

htop explained*

I was looking forward for web protocol, but alas...

tiffanyh2• 19 days ago

It was a typo. Thanks, fixed.

But there is an http headers article you might like.

https://peteris.rocks/blog/exotic-http-headers/

efxhoy• 19 days ago

Great job on getting the fixes merged!

drdexebtjl7• 19 days ago

I don’t understand the part about using heuristics and deciding what counts as used memory…

Used memory for the system is always total minus available.

Heuristics? I would hope that the system knows precisely what is using every single byte of physical and virtual memory. Is this a reporting problem? Why do we have to settle for heuristics and not the exact number?

CrociDB• 19 days ago

The thing is it's easy to define free, unused memory. But a lot of the used memory is your system caching stuff that would be free if you needed more than what's actually free. So you can see you have 1g of free memory out of your 4g, but then you allocate 3g and it will do without a sweat and you'd be confused. So you have to go and dig for what those caches are and report that they're effectively free too.

drdexebtjl7• 19 days ago

Instantly reclaimable disk caches should count as available, and they do.

This isn’t hard. The OS should just expose a counter for available memory instead of having applications understand every type of memory reservation.

edit:

Linux does this, but it has its own share of issues with memory counters. The “cached” memory includes tmpfs and ramfs for seemingly no reason.

man8alexd5• 19 days ago

You will be surprised by how inaccurate memory measurements are.

stephan-cr• 19 days ago

Not after reading this article. :-)

toast02• 19 days ago

I would hope that the system knows precisely what is using every single byte of physical and virtual memory.

Of course the system knows what is using every page. The difficulty is really in how to account for pages that are backed by disk.

If you count all of those as free, that's not accurate. If you count all of those as used, that's not accurate either. Additionally, FreeBSD (at least) doesn't have separate queues for disk backed pages, so there's not really a good way to know how much of your active (or inactive) memory is disk backed.

As an additional caveat that measuring active/inactive has costs. In the past, FreeBSD wouldn't really do the work for that until it needed to... I know some stuff changed, but I don't remember where it ended up; it wasn't great when it bulk marked a ton of pages as inactive and then the active ones would fault back in.

drdexebtjl7• 19 days ago

If you count all of those as free, that’s not accurate.

Why not? It depends on what you’re measuring. Physical memory? They count as free. Virtual memory? They count as used.

The ambiguities only arise when we stop making that distinction very clear.

jkrejcha3• 19 days ago

This is only really a problem if you accept overcommit as a force of nature that can't be changed or tweaked (you can still do address space reservation without needing overcommit)

If you don't, it becomes rather easy (and strict commit accounting is done for example on Linux even if it isn't used in some cases)

Memory mapped files can be entirely recreated from the disk so no need to charge for them. Anonymous pages (whether private or shareable) have to be charged. Shareable memory is the harder one to charge. (The case where a mapping is used by only one can get charged as private commit.) These two previous cases are charged even if in a swap file or whatnot

wolvoleo3• 19 days ago

I wonder if these btop fixes got into the standard ports collection? Or even upstream?

I like the command for viewing the ARC cache size, never knew that. It's only 2GB on my system (of 64GB RAM).

BSDobelix• 19 days ago

I like the command for viewing the ARC cache size

zfs-stats is also nice for more zfs internals like hit-rate L2 etc..

https://www.freshports.org/sysutils/zfs-stats

wolvoleo3• 19 days ago

Thanks! I didn't know that one.

JdeBP• 19 days ago

Ports is on 1.4.7.

* https://freshports.org/sysutils/btop/

The fix is still pending being even made to the origin version.

* https://github.com/aristocratos/btop/pull/1728

wolvoleo3• 19 days ago

Thanks! I will keep an eye on that.

haunter• 19 days ago

As for the “unauthorized” sign:

Book publishers used to print India/SEA-only editions of books only sold in those countries, significantly cheaper than in the US or Europe. Then a Thai guy realized that this would be a good business opportunity: buy cheaper books and then import them to the US. Wiley brought him to court, went to the SCOTUS, Wiley lost the case. So they ended up printing cheaper edition books.

https://en.wikipedia.org/wiki/Kirtsaeng_v._John_Wiley_%26_So....

Mind you "price discrimination" like this still exist in the digital world where locality is easier to be enforced. For example Steam has extensive regional pricing across countries so the same game can be significantly cheaper in Russia, India, Brazil etc. compared to US or EU

An example: https://steamdb.info/app/413150/

https://partner.steamgames.com/pricing/explorer

https://partner.steamgames.com/doc/store/pricing/currencies

Joker_vD4• 19 days ago

    When Kirtsaeng moved to the US in 1997 to pursue an undergraduate degree in mathematics at
    Cornell University,[4] he discovered that textbooks (not just those published by Wiley, but
    of other publishers too) were considerably more expensive to buy in the United States than
    in his home country. Kirtsaeng asked his relatives from Thailand to buy such books at home
    and ship them to him to sell at a profit. He sold the imported books on eBay, making $1.2
    million in revenue, although the parties disputed the net profit amount.

A text book case (ha!) about one of the mechanisms that enable the free markets and trade to bring the prices of goods down.

stavros2• 19 days ago

Wow, how did we go from "it's impossible to enforce region locking online because you can transmit information instantly across the world" to "locality more easily enforced in the digital world"?

exe342• 18 days ago

Most people haven't started using vpns yet.

vitally36432• 18 days ago

Silicon valley happened

regenschutz• 18 days ago

Wow, I've only ever heard of regional pricing being described as an overwhelmingly positive concept. When phrased as "price discrimination", it invokes a completely different set of (negative) emotions in me.

It's weirdly uncomfortable knowing that phrasing has such a big impact on one's emotions. It really shows how vulnerable we are to manipulation.

vitally36432• 18 days ago

That's why the current crop of authoritarian "think of the children" propaganda is so unreasonably effective

mewse-hn• 18 days ago

It's weirdly uncomfortable knowing that phrasing has such a big impact on one's emotions. It really shows how vulnerable we are to manipulation.

My dad would discuss it in high school english courses: terrorist vs freedom fighter etc

FreeBSD ate my RAM

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