Confusion regarding unit of RLIMIT_RSS

Confusion regarding unit of RLIMIT_RSS

[Lennart Poettering]

heya,

The man page for setrlimit() claims that RLIMIT_RSS is to be specified
in bytes, but glibc's bits/resources.h claims it was in bytes. My
suspicion is that the header is right, and the man page wrong. But of
course, since the limit has no effect on Linux anyway, maybe this is
not the most important thing to fix, but I thought I'd at least report
the discrepancy here...

Thanks,

Lennart
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Re: Confusion regarding unit of RLIMIT_RSS

[Michael Kerrisk (man-pages)]

Hi Lennart

On 11/09/2015 05:07 PM, Lennart Poettering wrote:
> heya,
> 
> The man page for setrlimit() claims that RLIMIT_RSS is to be specified
> in bytes, but glibc's bits/resources.h claims it was in bytes. 

I'm confused by that sentence. You have a "but", but both cases are
"bytes". What's the contradiction you are trying to point out?
Ahhh -- I get it now. The man page says "pages".

> My
> suspicion is that the header is right, and the man page wrong. But of
> course, since the limit has no effect on Linux anyway, maybe this is
> not the most important thing to fix, but I thought I'd at least report
> the discrepancy here...

The man page is clearly wrong. From bits/resources.h we have:

[[
  /* Largest resident set size, in bytes.   <=====
     This affects swapping; processes that are exceeding their
     resident set size will be more likely to have physical memory
     taken from them.  */
  __RLIMIT_RSS = 5,
#define RLIMIT_RSS __RLIMIT_RSS
]]

And in the kernel source file fs/proc/base.c, we have:

        [RLIMIT_RSS] = {"Max resident set", "bytes"},

As you note, the point is kind of moot, but the page should be fixed.
Done! 

Thanks for the report,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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