Fix KB conversion for memory in Windows

[oraclerob]

Fix to divide the bytes output from the GlobalMemoryStatusEx(&mut mem_info) function by 1024 to get the correct KB usage for the system.

[GuillaumeGomez]

Based on https://docs.microsoft.com/en-us/windows/win32/api/psapi/ns-psapi-performance_information, PageSize is in bytes so this conversion is invalid.

[GuillaumeGomez]

And based on this page: https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/ns-sysinfoapi-memorystatusex, it's all in bytes so this conversion is unneeded as well.

[GuillaumeGomez]

An important thing to note: sysinfo is using KB, not KiB, hence the 1000 divisions.

[oraclerob]

Yes, but your own example is listing these in KB and you end up with more memory than is actually installed. It doesn't look right. This is a contentious issue, but most systems assume a KB is 1024 bytes and not 1000 but I know there is a metric equivalent. Up to you. but on my Windows system I end up with more memory listed than installed. I'll pull the PR.

println!("total memory: {} KB", sys.total_memory());
println!("used memory : {} KB", sys.used_memory());
println!("total swap : {} KB", sys.total_swap());
println!("used swap : {} KB", sys.used_swap());

[GuillaumeGomez]

A KB is never 1024 unless it is a kikibyte (as opposed to kilobyte). There is a big confusion around KiB and KB because sometimes KiB is written Kb (even saw KB...).

Yes, but your own example is listing these in KB and you end up with more memory than is actually installed.

Do you have a screenshot with the complete display of your installed RAM? Because they tend to round it.

[oraclerob]

If you have a look at this wiki page, it does say at the bottom that MS tend to display in 1024 units.

https://en.wikipedia.org/wiki/Kilobyte

To be honest, I can't be bothered arguing about this and I'm happy to close this as I can spend my time on other projects. Incorporating windows-rs crate into this project (which API call gives me the correct answer) means we will need to rename the windows directory because there is a name conflict in the lib.rs namespace so I thought this would be the easiest option to display the correct amount of windows memory. Sadly I won't be able to use this tool for windows.

[GuillaumeGomez]

To be honest, I can't be bothered arguing about this and I'm happy to close this as I can spend my time on other projects. Incorporating windows-rs crate into this project (which API call gives me the correct answer) means we will need to rename the windows directory because there is a name conflict in the lib.rs namespace so I thought this would be the easiest option to display the correct amount of windows memory. Sadly I won't be able to use this tool for windows.

Except the memory returned by sysinfo is valid, just not in the unit you want. The conversion between the two is pretty simple though: mem * 1000 / 1024. It seems pretty minor but in the end it's up to you. sysinfo explicitly provides memory size in kilobytes so there is no reason that Windows would stand on its own apart from the other systems in that regard.

I'll be closing this then. Thanks for taking the time to look into it.

[NaokiM03]

@GuillaumeGomez

Hello.
Sorry for my poor English.

I also faced the same problem.
The Examples below divide by 1024 to convert bytes to KB. So, I think it would be better to use 1024 instead of 1000 in Windows.

// Use to convert bytes to KB
#define DIV 1024

https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-globalmemorystatusex

[GuillaumeGomez]

It's not KB, it's KiB. A common confusion, so no. If you want KiB, then * 1000 / 1024.

[NaokiM03]

Okay.
On Windows, KiB is almost always written as KB.
I understood that the decision was made not to follow that convention for this crate.

I'm sorry, if it's KB, it should be divided by 1000. I was wrong.

[GuillaumeGomez]

Windows documentation is making this very awkward and I find it really bad for readers comprehension but not much we can do about it unfortunately...