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Similarly, there are many annoying Linux bugs:

`pthread_create` can sometimes return back a garbage thread value or crash your program entirely without any way to catch it or detect it [1]. High speed threadding is hard enough as it is, without the kernel acting non-deterministically.

Un-killable processes after copy failure (D or S state) [2]. If the kernel is completely unable to recover from this failure, is it really best to make the process hang forever, where your only available option is to restart the machine? I ran into this with a copy onto a network drive with a spotty connection, that actual file itself really didn't matter - but there was no way to tell the kernel this.

Out Of Memory (OOM) "randomly" kills off processes without warning [3]. There doesn't appear to be a way to mark something as low-priority or high-priority and if you have a few things running, it's just "random" what you end up losing. From a software writing stand-point this is frustrating to say the least and makes recovery very difficult - who restarts who and how do you tell why the other process is down?

[1] https://linux.die.net/man/3/pthread_create

[2] https://superuser.com/questions/539920/cant-kill-a-sleeping-...

[3] https://serverfault.com/questions/84766/how-to-know-the-caus...

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Point 3 is wrong. OOM killing is not random. Each process is given a score according to its memory usage, and the highest score is chosen by the kernel. The way to mark priority in killing is to adjust this score through /proc. All of this is documented in `man 5 proc` from `/proc/[pid]/oom_adj` to `/proc/[pid]/oom_score_adj`.

http://man7.org/linux/man-pages/man5/proc.5.html

> OOM killing is not random.

Yeah I know, hence the use of "random".

> The way to mark priority in killing is to adjust this score through /proc.

Haven't heard about this, thanks for the heads up!

> > The way to mark priority in killing is to adjust this score through /proc. > > Haven't heard about this, thanks for the heads up!

While going down that road is technically correct, it is a road full of pain.

A slightly less painful strategy is to disable overcommit. That way, if memory pressure is high, and a process calls `malloc`, that call will fail if there is not enough memory, and that process will fail. If you only have a couple of processes in your system that are using most of the memory and you can control them, it is simpler to just making them resilient to these kind of errors, than to try to mess with the process score to control the OOM killer.

But any process can be trying to allocate at the time your system runs out of memory, and most applications are not authored to handle malloc failing. Process failure seems easier to work around, from what I’ve seen. Would love to hear more from someone who has contrary experience.

At least you can then properly blame the software for doing the wrong thing and potentially patch it. The kernel should not implement global behavior that encourages improper memory allocation failure handling.

Yes so much. The overcommit approach seems to be to say, “Most people are lazy so we shouldn’t allow anyone to brush their teeth.” Handling malloc failures isn’t rocket science.

Incorrectly handling malloc failures has been responsible for a lot of security problems. We are all better off acknowledging that C programmers are broadly incapable of writing correct OOM handling at scale and figuring out what to do with this fact, instead of wishing that it weren't this way.

Do you have an example of a nontrivial user-space project that has malloc failure handling that actually works, with tests and all? The one I'm aware of is SQLite. Then there is DBus, whose author disagrees with your assessment.

https://blog.ometer.com/2008/02/04/out-of-memory-handling-d-...

Lua, various OS kernels

Like any aspect of writing software, how you approach the problem effects the complexity of the final product. If someone doesn't make a habit of handling OOM, then of course their solutions are going to be messy and complex; they're going to "solve" the problem in the most direct and naive way, which is rarely the best way.

For example, unless I have reason to use a specialized data structure, I use intrusive list and RB-tree implementations, which cuts down on the number of individual allocations many fold. Once I allocate something like a request context, I know that I can add it to various lists and lookup trees without having to worry about allocation failure. Most of my projects have more points where they do I/O operations than memory allocations. Should people just ignore whether their reads or writes failed, too?

The JVM, and any other runtime which allocates its heap up front. You could argue that's cheating, but it does give you predictable behaviour.

Unfortunately, the fork/exec method of spawning processes doesn't work for memory heavy processes (such as say a java server) without overcommit and copy-on-write memory. Not that I think fork/exec is the best method to spawn processes, but it is the standard way in unix-like systems.

The rationale for disabling overcommit only really makes sense if physical and virtual memory consumption are in the same ballpark. That's true for some workloads but not generally true.

There are totally legitimate use cases for processes that use significantly more virtual memory than physical memory (since virtual memory is relatively cheap, but physical memory isn't). A lot of programs are going to touch and not release all virtual memory they allocate from the kernel, but there are plenty of important counterexamples.

fork()/exec() is one example (which I've been burned by personally), but there are plenty of others. Any program that uses TCMalloc and has fluctuating memory consumption will have a lot of virtual address space allocated but not backed by physical pages. Sophisticated programs like in-memory caches or databases can also safely exploit a larger virtual memory space while keeping the amount of physical memory bounded.

Virtual memory and overcommit isn't the same thing. Virtual memory means using disk space as memory. Overcommit means that the OS allows more memory to be allocated than it can guarantee is available. It is exactly like an airline booking 1 000 passengers for a flight with 500 seats, hoping that only half of them will actually show up. I don't think overcommit is ever needed in a modern system or is even a useful feature. For example, Windows doesn't support it at all.

Windows supports overcommit, it's just not the default, and it's not how typical Windows runtimes allocate memory. And the nice thing about making it opt-in is that processes which didn't ask for overcommit won't get shot down when overcommitted memory can't be faulted in.

No, it doesn't. See quotemstr's explanation here https://lwn.net/Articles/627632/

Thank you for the clarification.

What's left out, though (and perhaps the source of my confusion), is that you typically commit a reserved page from an exception handler, and if the commit fails then presumably in the vast majority of situations the process will simply exit. See https://docs.microsoft.com/en-us/windows/win32/memory/reserv...

If the code dereferencing the reserved-but-uncommitted memory was prepared to handle commit failure beforehand it would normally have done so explicitly inline. I can't imagine very many situations where I would pass a pointer to some library expecting the library to handle an exception when dereferencing it. There are some situations--and they're one reason why SEH is better than Unix-style signals--but extremely niche.[1]

Either way, my point was that Windows does strict accounting, and while you can accomplish something like overcommit explicitly, nobody else has to pay the price for such a memory management strategy. Only the processes gambling on lazy commit end up playing Russian Roulette.

[1] In a POSIX-based library I once used guard pages, SIGSEGV handler, per-thread signal stacks, and longjmp to implement an efficient contiguous stack structure. This was in an extremely performance critical loop (an NFA generated by Ragel) where constantly checking memory bounds on each push operation had substantial costs (as in multiples slower). AFAICT, it was all C and POSIX compliant. (Perhaps with the exception of whether SIGBUS or SIGSEGV was delivered.) Though, because neither POSIX nor Linux support per-thread signal handlers you could effectively only use this trick in one component of a process--you had to hog SIGSEGV handling--without coordination of signal handlers. SEH would have resolved this dilemma. This being such a niche use case, that wasn't much of a problem, though.

> I don't think overcommit is ever needed in a modern system or is even a useful feature.

If you want to spawn child processes from a process that uses half the system's memory (not uncommon in server environments) using fork/exec it is useful. In case you aren't familiar with how that works, the parent process makes copy of itself, including a virtual copy of all the memory assigned to that process. That memory isn't actually allocated or copied until the child process child tries to write to it (and then only the specific pages that are written to). Typically, the child process then calls `exec` to replace itself with a new program and replaces the process memory. Without overcommit or swap if the parent process is large enough, then the fork syscall fails due to insufficient memory.

In a desktop environment using swap/virtual memory is fine. But in a server environment, where the disk may be network-attached (higher latency) and just big enough for the OS and applications, needing significant swap space is often undesirable.

That is solved by adding a reasonable amount of swap space. In practice the swap will never be used, but it's there as a buffer to guarantee that things will work if the forked process doesn't immediately exec.

I haven't toyed with that in a long time (probably about a decade really) but back when I did it was still very difficult to get the OOM to behave the way you wanted. IIRC the scoring is fairly complex and take child processes into account so while it's technically completely deterministic it can still be fairly tricky to anticipate how it's going to work out in practice. And I did know about `oom_adjust`. Often it worked. Sometimes it didn't. Sometimes it would work too well and not kill a process that was clearly using an abnormal amount of memory. Finding the right `oom_adjust` is an art more than a science.

Overall I ended up in the camp "you shouldn't throw passengers out of the plane"[1]. The best way to have the OOM killer behave well is not to have it run at all. If I don't have enough RAM just panic and let me figure out what needs to be done.

[1] https://lwn.net/Articles/104185/

And the OOM Killer has been rewritten about twice entirely in the past decade. Christoph Lameter (one of my coworkers, who also wrote the SLUB memory allocator) wrote the very first one. Very little if any of his original code is in the current linux OOM Killer.

The current approach does indeed work much better. You can entirely disable the OOM Killer for a given workload with those procfs handles.

When I have multi-tenant shared servers that are regularly experiencing low memory conditions, that's now one of the first things that I turn off. I set sysctl vm.oom_dump_tasks=0 and vm.oom_kill_allocating_task=1, because without those and a comfortable amount of swap, I've found the likelihood that a rogue process uses up all the memory and the system becomes completely unrecoverable without power cycling, seemingly goes way up.

The way that the score is calculated, as I understand it, the processes with large memory footprints that are not particularly long-running, and especially not owned by root, are the most likely to be killed. My shared servers are running unicorn for Rails apps, so they almost all look the same under that lens.

I want the process with the runaway memory usage to be killed, so that person becomes aware of the problem when they find their app is down. (There are many better ways to solve this, but in our current system design, there's nothing to tell us that a service is down, so killing some other disused service means it's down until some user comes along and is impacted.) It seems like killing the process that made the last allocation is the most likely way to get this behavior I'm looking for, where the failures are noticed right away.

But I'm not convinced I've fixed anything, even if the behavior characteristics seem better, and I haven't had any servers going rogue and killing themselves lately, I am not the sysadmin, I'm pretty sure the sysadmin just comes and makes the machine over-provisioned so this doesn't happen again, which seems to be the best advice out there. And as I've learned from the discussion around this article, the fact of having a fast SSD on which paging stuff out and expiring it from the swap, all happens fast enough to look almost as memory, almost completely neuters the OOM anyway.

Our whole situation is wrong, don't even get me started; I'd like to solve this with containers, where we can set a policy that says "all containers must have memory request and limit" and thanks to cgroups, this problem never comes back.

> thanks to cgroups, this problem never comes back.

cgroups doesn't save you from the OOM killer. In fact, we're seeing persistent OOM issues in production even when there's more than enough physical memory to satisfy all allocation requests.

Similar to the issue discussed in the leading LKML thread, I/O contention and stalls when evicting pageable memory (e.g. buffer cache) can result in the OOM killer shooting down processes when an allocation request (particularly an in-kernel request, such as for socket buffers) can't be satisfied quickly enough--quickly according to some complex and opaque heuristics.

The fundamental problem is that overcommit has infected everything in the kernel. The assumption of overcommit is baked into Linux in the form of various heuristics and hacks. You can't really get away from it :(

There is now a way to mark processes as OOM-killer exempt

https://backdrift.org/oom-killer-how-to-create-oom-exclusion...

Part of the issue with processes stuck in D state (waiting for the kernel to do something) is that it is deeply tied into kernel assumptions about things like NFS, NFS is stateless, and theoretically severs can appear and disappear at will, and operations will keep working when it comes back. You can make NFS a hell of a lot less annoying in this regard by mounting it with soft or intr flags, however if the network disappears or hiccups, you WILL lose data (the network is NEVER reliable, in fact the entire model of NFS is arguably wrong to begin with)

> the entire model of NFS is arguably wrong to begin with

On local networks (everything attached to a single switch) with good hardware, it is reliable, and soft/intr is the worse choice among others.

To wit NFS is one of the commonly supported VM storage options (libvirt, VMware, etc).

Best of the bad options doesn't make it a good option. It's far from reliable and one of the most common reasons I encounter for deadlocked Linux systems. Well, to be fair, it also hangs a fair share of BSDs and sometimes even a Solaris. If at all possible, I'd suggest avoiding it.

What do you propose for a shared file system?

There is no use in specifying (no)intr as of kernel 2.6.25, it can always be interrupted by sigkill. See e.g. https://access.redhat.com/solutions/157873

There are many things "known" about NFS that are legacy.

That's not a problem with NFS, that's a fundamental issue with computers. Things fail. Nothing protects you from losing data, your local log-structured filing systems won't save you either. They'll help you protect an existing state from corruption, but they don't protect you from loss.

That new request you just received when a hardware failure occurred? Say goodbye to it, you've no way of ensuring it will make it to storage when the disks have caught fire. Later on, when you've put out the blaze, all that algorithms can do is tell you when things started to get lost.

This is a bad excuse for the really flakey nature of nfs, other network filesystems do not have its issues.

Like which ones?

AFS is a good example of a network filesystem that takes properties of the network into account, however its a little weird and not fully compliant with POSIX filesystem semantics.

However, it scales like crazy and is very powerful and reliable.

I ran AFS for very long, it does have issues which perhaps other network fs'es don't even notice. It has issues with clients behind NAT for instance, the callbacks won't work. The limit of files in a dir is less than for local filesystems (or were) so Maildirs with long mail filenames could get into something that feels like "out of inodes but not space" situations. All in all, it was very nice though.

What you are talking about is unrelated to NFSs broken model. Although still important, because these are the reasons why we don't need fsync() to actually flush data to disk for example, it can be asynchronous and only needs to add a checkpoint to your log structured filesystem that will be written to disk later, once enough data is buffered or long enough time has passed.

Often ordering would be enough, but sometimes you do want to wail until the changes are on disk. It's a mess.

What are you referring to regarding pthread_create()? Last time I checked I thought that it would return an undefined thread* only when giving a nonzero return code, which while certainly isn't handled in a lot of multi-threaded applications could be checked before anything else is done with the newly created thread.

There appears to be cases under high create/destroy scenarios where it returns zero, but failed to allocate memory for a thread during create. This is with tonnes of available memory (hence not a mapping error) and no exceptions thrown.

That said, it's still entirely possible I've made a mistake. Please see here: https://github.com/electric-sheep-uc/black-sheep/blob/master...

The idea is that you do preliminary processing of a camera frame before sending a neural network over the top.

> This is with tonnes of available memory (hence not a mapping error) and no exceptions thrown.

Could be a memory fragmentation issue

EDIT: Also since you're using C++ threads: You should really use move semantics, because right now you have two points of failure acting on the same thing: `new` operator may fail on creating the threads instance, and the underlying pthread_create may fail as well.

Comment on my mentioning on move semantics, because I feel that this really ought to be pointed out:

In all the C++ standard library implementations of std::thread the only member variable of that class is the native handle to the system thread itself; there are no additional member variables! This means that the size of a std::thread object is equal to the size of a native handle, usually the size of a pointer, but sometimes smaller.

If you create std::thread by `new` you're essentially creating a pointer to a "possibly a pointer", which comes with all the inefficiencies associated with it: Double indirection, small size allocations tend to fragment memory. And at the end of the day to actually use it, you have to at least lob around that outside pointer around on the stack anyway.

So there is zero benefit at all of using dynamic allocation for std::thread. Don't do it! Just create the std::thread instances on the stack, they're just handled/pointers with "smarts" around them, and you can copy them around just efficiently as you can copy a pointer or an integer. Better yet, if you're not trying to "outsmart" the compiler you'll often get copy elision where applicable.

sts::thread has its copy constructor deleted. This means that creating it on the heap is often your only option if you have to mix it with other types that don't handle noving properly because move semantics are strictly opt in.

> std::thread has its copy constructor deleted

and for good reason

> your only option if you have to mix it with other types that don't handle moving properly

It's not the only option. The other option is to implement move semantics on the containing type. Properly implemented move semantics gives you assurance about ownership and that you don't use the tread interface inappropriately.

Deleting the copy constructor is a very arbitrary design devision without any good reason.

Move semantics are a can of worms in themselves. You assume in your comment that you can modify the other types that interact with the types that are only movable. This is only possible if you own all relevant types, which is actually the exception rather than the norm. And even if you own the relevant related types, move semantics transitively enforce themselves onto containing types which turns their introduction into sprawling mess of cascading changes with hidden surprises.

Here's something to ponder on: What are the proper semantics for copying a thread? What is it you want to express by doing that?

You'll find that usually the copy constructor has been deleted only for those classes where the semantics of a copy are not well defined.

So let's assume you work around that by encapsulating that thread in a std::shared_ptr or a std::weak_ptr. What are the constraints you must work within when using that thread reference?

Usually when you run into "problems" caused by an object not being "move aware" triggered by encapsulating a non-copyable type, this is a red flag that something in your codes architecture is off. Think of it as a weaker variant of the strong typing of functional languages. You probably don't want to have a shared_ptr on a thread inside your object (and the object being copyable), but wrap that object in a shared_ptr (or weak_ptr) and pass those around.

Yourncery first question is already leading you down the wrong path: std::thread is a thread handle, not the thread itself. Equating the handle with the thread (a complex construct of a separate stack, seperate processor state, separate scheduling state etc.) is folly.

There are more software architectures between heaven and earth than exist in your philosophy. C++ especially is an old language and most code was written before C++11 started to be adopted. So a pure C++11 style codebase that follows the associated design best practices may be able to deal with std::thread and similarly restricted classes with little friction. But this just isn't the norm. Most big important codebases are too far down different roads to adjust them to play nice with move semantics.

> std::thread is a thread handle, not the thread itself

While technically true, semantically there's not much of a difference. Yes, you can copy around a handle, but then you have the burden of tracking all of these copies, so that you don't end up with a dangling handle to a thread long dead… or even worse, a reused handle for an entirely new thread that happens to have gotten the same handle value.

This is why you should not think of std::thread being a handle, but the actual thread. Yes, from a system level point of view there's the handle, and all the associated jazz that comes with threads (their dedicated stacks, maybe TLS, affinity masks, etc.), all of which are non-portable and hence not exposed by std::thread, because essentially you're not supposed to see all of that stuff.

> C++ especially is an old language and most code was written before C++11 started to be adopted.

That is true. Heck, I've still got some C++ code around which I wrote almost 25 years ago. But if you use a feature that was introduced only later, then you should use it within the constraints supported by the language version that introduced it and not shoehorn workarounds "just to make it work".

std::thread is just fundamentally flawed. The way it encapsulates the thread itself is just one of the things. Thread CPU affinity cannot be managed. Code cannot query which thread it is running on. There are no thread ids (the handle would be a workable substitute if it were copyable). Threads cannot be killed. In other words, if you take threading seriously std::thread is useless.

I need all of these things except for killing threads. So this is not just an academic list for me.

> Thread CPU affinity cannot be managed

That's because the capability of doing so depends on the target environment. C++ is all-target. If you need that you can use `std::thread::native_handle` + the OS's API for that.

> Code cannot query which thread it is running on

You're wrong assuming that. std::this_thread::get_id() exists: https://en.cppreference.com/w/cpp/thread/get_id

> There are no thread ids

Yes, there are. std::thread::get_id() exists (also see above): https://en.cppreference.com/w/cpp/thread/thread/get_id

> Threads cannot be killed.

Not all runtime environments actually support doing this kind of thing. Also within the semantics of C++ the ability to kill threads opens an gargantuan can of worms. For example how would you implement RAII style deallocation and deinitialization of objects created within the scope of a thread?

Or even one lower level: How do you deal with locks held within such a thread? Not all OS's define semantics on what to do with synchronization objects that a held in a thread that's been killed. Window implicitly releases them. Pthreads defined mutex consistency, but after killing a thread holding a mutex, the state of the affected mutex is indeterminate until a locking attempt on the mutex is done.

Killing threads really is something that should be avoided if possible. Not since C++11 but since ever, because it causes a lot more problems than it solves. If you need something that can be killed without going through too much trouble, spawn a processes and use shared memory.

std::thread is very limited because C++ is an all-purpose, all-operating-system, all-environment language and it must limit itself to greatest common denominator of threading support you can expect. And realistically this boils down to: 1. there are threads. And 2. threads are created, run for some time, may terminate and you can wait for termination.

That's it. Anything beyond that is utterly dependent on the runtime environment. And because of that std::thread does give you std::thread::native_handle, to be able to interface with that.

Many features of the STL are optional. So the existence of operating systems that are incapable of providing certain features is not a valid argument for leaving out features that are essential to using threads in any meaningful way on others.

Killable threads are not rocket science, either. You're just limited in the kinds of things these threads can do. But there's no need to get all hungup on that particular feature.

> Please see here: https://github.com/electric-sheep-uc/black-sheep/blob/0735de...

Creating and destroying threads in a tight loop (and blocking on their destruction, thereby reducing the point of having many) seems like a bad idea. Conceptually you have only maximum of two threads in any given part of this snippet, the one running the loop and the current instance of visThread. My guess is also that the loop thread spends most of its time waiting for the recently created threads to die. Why not have visThread only get created once and process a queue of events?

Anyway without additional evidence you potentially flagged a bug in the c++ standard library rather than pthread_create.

Firstly, thanks for taking the time to look.

> Creating and destroying threads in a tight loop (and blocking on their destruction, thereby reducing the point of having many) seems like a bad idea.

The purpose is that it's pretty much 100% always running a visThread (it's a neural network that takes about 100ms per image). The pre-process on the other hand runs in about 10ms, but there's no reason why it can't be run in advance (+). The neural network can't really be run on multiple cores safely, but it does have OpenMP (parallel loops).

(+) It does create some latency in the output compared to the real world, but it's not a massive deal when it comes down to it.

> Why not have visThread only get created once and process a queue of events?

This is probably the best way to do this, but this was the lazy way with not too much overhead (I think) :)

> Anyway without additional evidence you potentially flagged a bug in the c++ standard library rather than pthread_create.

Possibly, I did run it through GDB and Valgrind, it reliably seemed to die in pthread_create, but that of course could have only been the trigger. It could also be the aggressive optimization [1].

[1] https://github.com/electric-sheep-uc/black-sheep/blob/0735de...

What do you recommend doing when Linux Freezes? It doesn't come up a lot, but when it does it can be kind of unnerving since the three-finger-salute doesn't work.

I would also love to know if anybody has a solution for getting video to play properly in Firefox. I know it's not a bug per se, but it would be nice to not have to switch between browsers all the time.

I've been using Ubuntu for about a year now and otherwise its been a very positive experience.

> What do you recommend doing when Linux Freezes? It doesn't come up a lot, but when it does it can be kind of unnerving since the three-finger-salute doesn't work.

Unfortunately, I don't really have a solution for this. I have an SSD as the main disk and _even now_, when I hit this too hard Linux grinds to a halt. No mouse, no keyboard, just heat, fans and disk light.

One thing that sometimes works for me is the old CTRL+ALT+FX mashing, but not always. Once you can get a shell you can type into you're okay, but of course this doesn't always work.

> I would also love to know if anybody has a solution for getting video to play properly in Firefox. I know it's not a bug per se, but it would be nice to not have to switch between browsers all the time.

What do you mean? It's been reliable for quite a long while? There were two issues I used to have, one was not having my graphics card setup (it was running from the CPU) and the other was not having flash (when that was something).

> I've been using Ubuntu for about a year now and otherwise its been a very positive experience.

Yeah, I think it makes one of the better daily drivers.

Thank you for your answer. It's good to know that dealing with freezes is not a problem only faced by newbs like myself.

Re: playing video, for some reason I can't play South Park on either Firefox or Chrome. Videos on twitter also won't load with Firefox, though they work fine with Chrome.

> Thank you for your answer. It's good to know that dealing with freezes is not a problem only faced by newbs like myself.

Yeah, it's another bug with Desktop based Linux. The problem is that Linux "basically" treats the GUI like any other program, when things get heavy everything gets roughly evenly screwed. OSes designed to be centralized around a GUI on the other hand usually guarantee that GUI related processes get a minimum amount of time on the CPU to ensure they don't freeze.

Linux should 100% be doing this. Doing lots of hardware I/O shouldn't mean you lose the mouse or keyboard. When you lose control of input, you think the machine isn't doing something, when in actual fact it's doing tonnes, it's just not showing you. Even something like Android suffers from this under heavy load, it's really crap.

The real joke is, it's probably a difficult kernel fix. You would need some kind of watch dog timer for the kernel to make sure it's not getting too bogged down with any one particular task and then interrupt ones that are (some tasks don't like to be interrupted) [1]. You then need make sure that all of the heavy kernel calls don't make guarantees about the call being completed (i.e. blocking), which to be completely honest should be the default position to take anyway.

I'm not completely up-to-date on this, but my bet is that the issues come from everywhere. Programs can read/write arbitrarily large amounts of data (RAM, disk, network, bus, etc), when I believe you should be able to ask the kernel what size it would like you to read/write based on I/O activity and the capabilities of the device. If your program is bogging down the kernel, it should lover your recommended block read/write size. Better yet, this would be compatible with existing software, as they could choose to ignore this, possibly with it "punishing" programs that eat up lots of kernel time by making them wait longer for their next opportunity. There's a bunch of algorithms for time splicing tasks, but the most optimal appears to be max-min with very little organizing overhead [2].

> Re: playing video, for some reason I can't play South Park on either Firefox or Chrome. Videos on twitter also won't load with Firefox, though they work fine with Chrome.

Hmm, that shouldn't happen, sounds like you potentially have some system-wide badness. A few things to try:

* Disable any customization you made (extensions, add-ons, etc) - see if it is one of these interfering

* Make sure you have all updates and you're running an up-to-date version of Ubuntu (this issues have possibly been patched already)

* Make sure you have the correct drivers installed for your GPU

But... One thing I did note was that JavaScript coin miners have gotten so bad that I can't run certain sites without ad-blockers anymore (uBlock Origin is generally recommended). I remember my CPU sitting at one core maxed out just because of the JS engine. I generally run uBlock Origin + NoScript on every page and manually enable temporary scripts on pages I trust. One of the biggest offenders for crazily heavy JS was actually Facebook.

[1] https://en.wikipedia.org/wiki/Watchdog_timer

[2] https://uhra.herts.ac.uk/bitstream/handle/2299/19523/Accepte...

I thought about your comment re: video and I did some more poking around online since I was hoping to avoid having to do a fresh install. I tried updating my video codecs and now Netflix/Hulu works! Hooray!

>> JavaScript coin miners have gotten so bad that I can't run certain sites without ad-blockers anymore

Whoa, is that the reason why some websites are eating a ton of memory?? Is this common?

>> I generally run uBlock Origin + NoScript on every page and manually enable temporary scripts on pages I trust.

Thank you for the recommendations, I'll check those out.

> I thought about your comment re: video and I did some more poking around online since I was hoping to avoid having to do a fresh install. I tried updating my video codecs and now Netflix/Hulu works! Hooray!

Yeah, it's important to pull updates regularly :) In general many of the bugs you'll come across will end up being fixed sooner or later, so it's worth checking regularly.

> Whoa, is that the reason why some websites are eating a ton of memory?? Is this common?

That and just the poor use of JS. Most websites really don't need JS. I use mbasic.facebook.com instead of facebook.com as it'll run without JS, plus you have to manually refresh to get any kind of notification.

One of those magic sysrq combination used to work for me. I used to use it a lot before I upgraded to 12 GB RAM.

I have to say, reading all these replies about the OOM killer makes Linux look quite bad. These proc scores are not an elegant solution. I far prefer Darwin’s launchd which lets you set actual memory limits (soft and hard) that gives you warnings before you cross a threshold. Now this is more consumer OS oriented, but something equivalent for servers that let you express preferences in a more natural way seems desirable.

memory limits are also available in linux via cgroups or ulimit.

You can use ulimit to set soft and hard limits for all sorts of system resources (including memory) on Linux.

True — I forgot about this. But can you do that on a process via some config _before_ the process is created?

Yeah, usually you call ulimit before calling the process. The new process inherits the limits. If you want to modify the limits of an _existing_ process, you can use prlimit.

..but if the problem is programs not checking malloc() return codes since it will not return failures, then ulimits will in themselves not help the program. It will help the OS to stay alive which is good, but we still need to deal with the programs who expect to run all the way into a swamp and sink without malloc giving them "bad news".

systemd lets you configure soft and hard limits on a per-service level, almost identically to launchd. See MemoryHigh= and MemoryMax= [1].

This does depend on cgroupsv2, but it works on most modern distros.

[1]: https://www.freedesktop.org/software/systemd/man/systemd.res...

Oh nice! Thanks for the pointer!

There is nothing more frustrating than unkillable processes stuck io iowait(D) state. There's no reason for this behavior to exist. And its so easy to hang forever - network blink, your NFS client gets stuck and your programs too.

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