gzip and swap test

gistfile1.txt

# match media01
sudo sysctl vm.swappiness=0
sudo echo 2 > /proc/sys/vm/overcommit_memory
sudo echo 50 > /proc/sys/vm/overcommit_ratio

vim /memtest.sh
#!/bin/bash
D=/tmp/$1
mkdir $D
mount -ttmpfs $D $D # by default is sized to half of physical memory
dd if=/dev/zero of=$D/test bs=1M # will fill that partition
:wq
/memtest.sh a # fill first half of physical memory
/memtest.sh b # fill second half of physical memory
/memtest.sh c # overcommit beyond physical memory
/memtest.sh d # overcommit beyond physical memory even more
# continue on...
# normally machine freezes once swap is full
# but notice that swap still fills according to vm.swappiness

root@all-in-one01:/tmp# cat /dev/zero | gzip > test                                                       │

# notice that at no point (with any settings) does gzip cause swap usage

i was able to use
swapoff -a
and the tmpfs never went into swap.

see also: http://serverfault.com/questions/372020/what-are-the-best-possible-ways-to-benchmark-ram-no-ecc-under-linux-arm