[Buildroot] Weird OOM problem

Patrick Doyle wpdster at gmail.com
Wed Nov 7 15:07:54 UTC 2018

Hello fellow buildrooters.
I know this is the wrong list on which to ask this question, but you
are all experts in this field and can probably either direct me to the
proper list, or give me some tips here.  (After all, this is where I
hang out).

I have an embedded system with 128MB of RAM and no SWAP.

/tmp is mounted on a tmpfs

Shortly after boot, I can log in and look at how much memory is free:

# free
             total       used       free     shared    buffers     cached
Mem:        120912      45224      75688        100       7700      17900
-/+ buffers/cache:      19624     101288
Swap:            0          0          0

I create a 25MB file in /tmp, and look again:
# dd if=/dev/urandom bs=1M count=25 of=/tmp/foo
25+0 records in
25+0 records out
# free
             total       used       free     shared    buffers     cached
Mem:        120912      53620      67292      25700       1040      33324
-/+ buffers/cache:      19256     101656
Swap:            0          0          0

If I try to create a 2nd 25MB file (or even an 8MB file) in /tmp, then
the OOM killer kicks in, despite the cat that I have somewhere between
67 and 101MB free.

It would appear that the OOM killer kicks in when the disk cache (aka
"shared") grows beyond 25% of total RAM.

Is that true?  Can I tune that?

I am going to keep looking on my own now that I have learned this
much, but I figured I would put the question out to the experts in the
mean time.

Thanks for any tips you can give me, (even if the tip is, "Go ask SO").


More information about the buildroot mailing list