Does 'ulimit -m' not work on (modern) Linux?

Question

This article claims that the -m flag to ulimit does nothing in modern Linux. I can find nothing else to corroborate this claim. Is it accurate?

You may try to limit the memory usage of a process by setting the maximum resident set size (ulimit -m). This has no effect on Linux. man setrlimit says it used to work only in ancient versions. You should limit the maximum amount of virtual memory (ulimit -v) instead.

If it's true that it worked in older versions of Linux, which version stopped supporting this?

Here's an interesting article which goes into some detail about the various limits and what they mean. It's ten years old but presumably most of this stuff doesn't change. http://answers.google.com/answers/threadview/id/311442.html — Dan Pritts, Oct 06 '14 at 16:42
Related: [Limit memory usage for a single Linux process](http://unix.stackexchange.com/q/44985/1174) — Cristian Ciupitu, Apr 29 '16 at 22:50

Cristian Ciupitu · Accepted Answer · 2020-11-25T14:58:22.450

17

It says right there in the article:

This has no effect on Linux. man setrlimit says it used to work only in ancient versions.

The setrlimit man page says:

 RLIMIT_RSS
        Specifies the limit (in pages) of the process's resident set
        (the number of virtual pages resident in RAM).  This limit has
        effect only in Linux 2.4.x, x < 30, and there affects only
        calls to madvise(2) specifying MADV_WILLNEED.

So it stopped working in 2.4.30. The changelog for 2.4.30 says something about this:

Marcelo Tosatti:
o Ake Sandgren: Fix RLIMIT_RSS madvise calculation bug
o Hugh Dickins: remove rlim_rss and this RLIMIT_RSS code from madvise. Presumably the code crept in by mistake

edited Nov 25 '20 at 14:58

answered May 15 '14 at 21:05

Cristian Ciupitu

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Thanks. I looked through the setrlimit page, but didn't know what to look for. – Flimzy May 15 '14 at 21:10
You had to look for `resident` from *resident set size*. – Cristian Ciupitu May 15 '14 at 21:10

Does 'ulimit -m' not work on (modern) Linux?

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