4 ms·

Oh wow that is a really interesting test solution. That would be an interesting thing to add to all zig tests (I know they already have the testing allocator an

by olodus 3y ago

Oh wow that is a really interesting test solution. That would be an interesting thing to add to all zig tests (I know they already have the testing allocator and good valgrind support but I don't think that tests/simulates oom). I love things like these that use existing tests and expand the to just test further thing in already covered flows. We have done similar things at my work where we test expansion of data models against old models to check that we cover upgrade scenarios.

judofyr 3y ago
I've been using this helper: https://github.com/judofyr/zini/blob/ea91f645b7dc061adcedc91eaf252397b75d2323/src/utils.zig#L43-L55 https://github.com/judofyr/zini/blob/ea91f645b7dc061adcedc91.... It starts by making the first allocation fail, then the second, then the third, and so on. As long as it returns OutOfMemory (without leaking memory) then everything is fine.
squeek502 3y ago
There's support for exactly this type of OOM testing in Zig via std.testing.checkAllAllocationFailures: - https://github.com/ziglang/zig/blob/1606717b5fed83ee64ba1a91e55248e07a51afa6/lib/std/testing.zig#L972-L1124 https://github.com/ziglang/zig/blob/1606717b5fed83ee64ba1a91... - https://www.ryanliptak.com/blog/zig-intro-to-check-all-allocation-failures/ https://www.ryanliptak.com/blog/zig-intro-to-check-all-alloc...
- olodus 3y ago
  Oh cool, didn't know that. Thanks.
- astrange 3y ago
  This is a clear sign of a badly designed language. You should never see a fixed-size (less than page size) allocation fail, simply because there's nothing you can reasonably do if it does fail. Either you should crash or it should block until it is possible again. (Where crash means a worker process or something limited to something less than the entire system. See Erlang for the logical extension of this.) I realize this implies Windows and Java are badly designed and my answer to that is "yes".
  - matheusmoreira 3y ago
    So if my browser tries to allocate memory for a tab and the allocation fails it should just crash or block instead of handling the failure gracefully by not creating a new tab and telling me the system is running low on memory?
    - astrange 3y ago
      Tabs are separate processes in every modern browser. Actually since you skipped all the less than a page stuff I'm not sure you actually understand what my post is about…?
  - gnubison 3y ago
    Is Linux designed in such a way that less-than-page size allocations never fail? How would that work?
    - astrange 3y ago
      As long as the syscalls don't themselves fail, it's no problem until you run out of address space. At which point you should crash because you probably need to allocate to handle any reasonable errors.
      - cassepipe 3y ago
        So is there no point to checking malloc return ?

by olodus 3y ago

judofyr 3y ago

I've been using this helper: https://github.com/judofyr/zini/blob/ea91f645b7dc061adcedc91eaf252397b75d2323/src/utils.zig#L43-L55 https://github.com/judofyr/zini/blob/ea91f645b7dc061adcedc91.... It starts by making the first allocation fail, then the second, then the third, and so on. As long as it returns OutOfMemory (without leaking memory) then everything is fine.

squeek502 3y ago

There's support for exactly this type of OOM testing in Zig via std.testing.checkAllAllocationFailures: - https://github.com/ziglang/zig/blob/1606717b5fed83ee64ba1a91e55248e07a51afa6/lib/std/testing.zig#L972-L1124 https://github.com/ziglang/zig/blob/1606717b5fed83ee64ba1a91... - https://www.ryanliptak.com/blog/zig-intro-to-check-all-allocation-failures/ https://www.ryanliptak.com/blog/zig-intro-to-check-all-alloc...

olodus 3y ago
Oh cool, didn't know that. Thanks.
astrange 3y ago
This is a clear sign of a badly designed language. You should never see a fixed-size (less than page size) allocation fail, simply because there's nothing you can reasonably do if it does fail. Either you should crash or it should block until it is possible again. (Where crash means a worker process or something limited to something less than the entire system. See Erlang for the logical extension of this.) I realize this implies Windows and Java are badly designed and my answer to that is "yes".
- matheusmoreira 3y ago
  So if my browser tries to allocate memory for a tab and the allocation fails it should just crash or block instead of handling the failure gracefully by not creating a new tab and telling me the system is running low on memory?
  - astrange 3y ago
    Tabs are separate processes in every modern browser. Actually since you skipped all the less than a page stuff I'm not sure you actually understand what my post is about…?
- gnubison 3y ago
  Is Linux designed in such a way that less-than-page size allocations never fail? How would that work?
  - astrange 3y ago
    As long as the syscalls don't themselves fail, it's no problem until you run out of address space. At which point you should crash because you probably need to allocate to handle any reasonable errors.
    - cassepipe 3y ago
      So is there no point to checking malloc return ?