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PID is not respected on MacOS/Darwin platform #39

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edariedl opened this issue Apr 4, 2020 · 2 comments
Closed

PID is not respected on MacOS/Darwin platform #39

edariedl opened this issue Apr 4, 2020 · 2 comments

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@edariedl
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edariedl commented Apr 4, 2020 •
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get_process_mem always returns memory used by current process. It does not respect PID.

Here are some tests from irb

irb(main):001:0> require 'get_process_mem'
=> true
irb(main):002:0> GetProcessMem.new.kb
=> 17744.0
irb(main):003:0> `ps -o rss= -p #{Process.pid}`
=> " 17836\n"

but if I try to get memory of different process

irb(main):004:0> GetProcessMem.new(84330).kb
=> 17860.0
irb(main):005:0> `ps -o rss= -p 84330`
=> " 75104\n"

I'll get back the same amount of memory as I've got for the current process.

This issue was introduced by the pull request #32. Code for Darvin platform doesn't use PID to determine used RAM, it always returns used RAM for current process.
@schneems schneems changed the title PID is not respected on MacOS/Darvin platform PID is not respected on MacOS/Darwin platform Aug 25, 2020
schneems added a commit that referenced this issue Aug 25, 2020
@schneems
[close #39] Supporting different PIDs on Mac
b47816a 
Currently when you call `GetProcessMem.new` with a different pid value than the current process it calls `GetProcessMem::Darwin.resident_size this uses FFI to get data from the mach kernel about the current process.

- #32
- https://stackoverflow.com/questions/18389581/memory-used-by-a-process-under-mac-os-x/23379216#23379216

This PR adds a test to ensure that memory results from different processes is correctly reported.

This PR addresses the different PID problem by checking if a different pid other than Process.pid is being passed in. If that's the case then we will fall back to determining memory based off of shelling out to `ps`.

There was a performance concern over using `Process.pid` but it appears to be relatively fast. It is approximately the speed of allocating 3 string object.
@schneems
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I've got a workaround on #41

schneems added a commit that referenced this issue Aug 25, 2020
@schneems
Merge pull request #41 from schneems/schneems/fix-mac-pid-bug
a29c2f2 
[close #39] Supporting different PIDs on Mac
@schneems
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This is fixed and released in 0.2.6

@fcheung fcheung mentioned this issue Aug 27, 2020
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@schneems @edariedl