Possible working method to get actual process size on Linux

[Stefan Reich]

Yes, that sounds like a cleaner way. I do see these fields even on my
oldest kernel.

Let me guess, smem probably reads from /smaps too...

On Thu, 3 Oct 2019 at 16:15, Florian Weimer <fw at deneb.enyo.de> wrote:

> * Stefan Reich:
>
> > OK, here is the code:
> > https://github.com/stefan-reich/LinuxProcessSizeDetector
> >
> > Can this be linked somewhere? I believe it to be useful. Seems to work on
> > the machines I tested it on, even though there is mild guesswork
> involved.
>
> With a recent-enough kernel, you will see this:
>
> $ grep ^[^A-Z] /proc/21679/smaps | grep memfd | sort -k3
> 40000000000-40001000000 rw-s 00000000 00:05 253242
>  /memfd:java_heap (deleted)
> 80000000000-80001000000 rw-s 00000000 00:05 253242
>  /memfd:java_heap (deleted)
> 100000000000-100001000000 rw-s 00000000 00:05 253242
>  /memfd:java_heap (deleted)
> 7fffe000000-80000000000 rw-s 01000000 00:05 253242
>  /memfd:java_heap (deleted)
> bfffe000000-c0000000000 rw-s 01000000 00:05 253242
>  /memfd:java_heap (deleted)
> 13fffe000000-140000000000 rw-s 01000000 00:05 253242
>  /memfd:java_heap (deleted)
> 40001000000-40002000000 rw-s 03000000 00:05 253242
>  /memfd:java_heap (deleted)
> 80001000000-80002000000 rw-s 03000000 00:05 253242
>  /memfd:java_heap (deleted)
> 100001000000-100002000000 rw-s 03000000 00:05 253242
>  /memfd:java_heap (deleted)
> 7fffc000000-7fffe000000 rw-s 04000000 00:05 253242
>  /memfd:java_heap (deleted)
> bfffc000000-bfffe000000 rw-s 04000000 00:05 253242
>  /memfd:java_heap (deleted)
> 13fffc000000-13fffe000000 rw-s 04000000 00:05 253242
>  /memfd:java_heap (deleted)
> 40002000000-4000ec00000 rw-s 06000000 00:05 253242
>  /memfd:java_heap (deleted)
> 80002000000-8000ec00000 rw-s 06000000 00:05 253242
>  /memfd:java_heap (deleted)
> 100002000000-10000ec00000 rw-s 06000000 00:05 253242
>  /memfd:java_heap (deleted)
>
> That is, you can recover the information which mapping aliases which
> other mapping by looking at device/inode combination (column 4 and 5)
> and the mapping offset (column 3).
>
> I believe there is a tool called smem which does exactly that.
>


-- 
Stefan Reich
BotCompany.de // Java-based operating systems