| Does this result in programs more frequently erroring/crashing because they can't allocate? I don't know how well many of the programs I frequently use on my desktop (Firefox, GNOME desktop, JVM + IntelliJ, Slack, etc.) handle allocation failures. I'm not sure they would do much better than crash, but I know the default OOM killer settings work well for me. About once a year a real runaway process (usually a throwaway program I'm working on) gets OOM-killed, and that's fine with me. |
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| ▲ | swinglock 2 hours ago | parent | next [-] | | I don't think it has overcommit at all, at least that's the default. That would be why you don't have Windows OOM killer stories. | | |
| ▲ | tredre3 2 hours ago | parent [-] | | The reason you hear less about Window's OOM killer is simply because it works well. The Linux Kernel OOM killer kills random things. Userspace OOM killers are meant to improve this, and they work well in a server situation when you already know in advance what is likely to go haywire and what is safe to kill. But they don't work well on desktop (some of them are improving but it doesn't seem to be a priority). The Windows OOM killer by comparison usually kills something sensible (i.e. the program that is actually using all the memory), and asks the user for permission before killing it (when possible). You do see a lot of memes of situations where it fails. | | |
| ▲ | nok22kon 2 hours ago | parent [-] | | damn, good observation, when my data analysis python script goes wrong and allocates 24 GB of RAM on a 32 GB computer, it crashes (gets killed) with "out of memory" error. I've never seen something else getting killed |
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| ▲ | wongarsu 2 hours ago | parent | prev | next [-] | | Not overcommitting is Windows's default and only behavior A memory allocator can implement overcommit, because you can separate reserving virtual memory and having it backed by physical memory into two different system calls. But from the point of view of the kernel, any time it promises to give you physical memory that memory is backed either by RAM or by space reserved in the swap file | |
| ▲ | szmarczak 2 hours ago | parent | prev [-] | | Settings -> View advanced system settings -> Performance (Settings) -> Advanced -> Virtual memory (Change...) -> No paging file | | |
| ▲ | tredre3 2 hours ago | parent | next [-] | | That's disabling swap, not overcommit. Windows doesn't overcommit. It's one of the reason why it handles low memory situations so much more gracefully than Linux. | | |
| ▲ | 0x1d7 2 hours ago | parent [-] | | ^ The purpose of the system commit limit and commit charge is to track all uses of these resources to ensure they are never overcommitted — that is, that there is never more virtual address space defined than there is space to store its contents, either in RAM or in backing store (on disk).
- Windows Internals, 7th Edition |
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| ▲ | 0x1d7 2 hours ago | parent | prev [-] | | This is almost always a bad idea. If no memory is available where a page file would make a difference, this leads to application crashes instead. A crash is (usually) worse than paging. Certain applications, Photoshop being the historical example, will outright fail to run with no page file present. | | |
| ▲ | szmarczak 2 hours ago | parent [-] | | > this leads to application crashes instead Same happens if the page file is full. In that case, why don't those programs use disk directly instead? No such problem would've ever occured if programs hadn't allocated more than they actually use. | | |
| ▲ | toast0 an hour ago | parent | next [-] | | By default, windows uses an expandable page file. Typically, performance drops enough that the user kills the program or reboots before the page file expands to fill the disk. And other threads here suggest there is something that will prompt users to kill programs in states like this. > No such problem would've ever occured if programs hadn't allocated more than they actually use. That's part of the issue, but sometimes things do in fact use too much memory as well as allocate too much. Another part of the issue is that few programs are built to handle allocation failures. And then you have a metrics issue. There's not really a good metric to know when you're out of memory, other than performance collapse. If your applications don't use disk, it's not too hard; but when they do use disk, performance will collapse once there's insufficient memory to provide the disk caching needed. In my experience, adding a small swap and monitoring swap i/o can be pretty helpful, and a small swap doesn't tend to allow long thrashing when memory use grows. But that's not universal and everybody loves to hate swap these days. | |
| ▲ | 0x1d7 2 hours ago | parent | prev [-] | | Your argument falls flat when a page file can be multi-GB and automatically grow. And if your application admin was competent, memory monitoring would be part of the application monitoring stack. An application that grows in such a way (besides having backing stores for memory-mapped files, as well) will often perform so poorly that it requires addressing (adding RAM, looking for application faults, etc). A page file is insurance, one that can last you much longer than available system memory. | | |
| ▲ | szmarczak an hour ago | parent [-] | | > memory monitoring would be part of the application monitoring stack You don't need it if you have everything allocated upfront. TigerBeetle does this, everybody else can. Using something like Rust is already a huge win when compared to shipping a browser or running Node.js. > Your argument falls flat when a page file can be multi-GB and automatically grow This doesn't solve the original issue and only masks the underlying problem. |
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