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by ablob
447 days ago
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Memory is freed as soon as the program closes by the operating system.
If you have an open connection to a database they might expect you to talk to them before you close the handle (for example, to differentiate between crash and normal shutdown). Any resource shared between programs might have a protocol that needs to be followed which the operating system might not do for you. The GC model only cares about memory, so I don't really understand what you mean by "flawed for non memory use cases". It was never designed for anything other than managing memory for you. You wouldn't expect a car to be able to fly, would you? I personally like the distinction between memory and other resources.
If you look hard enough I'm sure you'll find ways to break a model that conflates the two. Similar to this, the "everything is a file" model breaks down for some applications. Sure, a program designed to only work with files might be able to read from a socket/stream, but the behavior and assumptions you can make vary. For example, it is reasonable to assume that a file has a limited size. Imagine you're doing a "read_all" on some video-feed because /dev/camera was the handle you've been given. I'm sure that would blow up the program. In short, until there is a model that can reasonably explain why memory and other resources can be homogenized into one model without issue, I believe it's best to accept the special treatment. |
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> Any resource shared between programs might have a protocol that needs to be followed which the operating system might not do for you.
Run far and quickly from any software that attempts to do this. It’s a sure fire indication of fragile code. At best such things should be restricted to optimizing performance maybe if it doesn’t risk correctness. But it’s better to just not make any assumptions about reliable delivery indicating graceful shutdown or lack of signal indicating crash.
> In short, until there is a model that can reasonably explain why memory and other resources can be homogenized into one model without issue, I believe it's best to accept the special treatment.
C++ and Rust do provide compelling reasons why memory is no different from other resources. I think the counter is the better position - you have to prove that a memory resource is really different for the purposes of resource management than anything else. You can easily demonstrate why network and files probably should have different APIs (drastically different latencies, different properties to configure etc). That’s why network file systems generally have such poor performance - the as-if pretension sacrifices a lot of performance.
The main argument tracing GC basically makes is that it’s ok to be geeedy and wasteful with RAM because there’s so much of it that retaining it extra is a better tradeoff. Similarly it argues that the cycles taken by GC and random variable length pauses it often generates don’t matter most of the time. The counter is that while it probably doesn’t matter in the P90 case, it does matter when everyone takes this attitude and P95+ latencies (depending on how many services are between you and the user you’d be surprised how many 9s of good latency your services have to achieve for the eyeball user to observe an overall good P90 score).
> For example, it is reasonable to assume that a file has a limited size. Imagine you're doing a "read_all" on some video-feed because /dev/camera was the handle you've been given. I'm sure that would blow up the program.
Right, which is one of many reasons why you shouldn’t ever assume files you’re given are finite length. You could be passed stdin too. Of course you can make simplifications in cases, but that requires domain-specific knowledge, something tracing GCs do not have because they’re agnostic to use case.