Si j'utilise ma machine [Ubuntu 16.04 64 bits, noyau 4.4] pendant un certain temps, QEMU a besoin que les caches du noyau soient supprimés, sinon, il n'arrivera pas à allouer la RAM.
Pourquoi cela arrive-t-il?
Voici un exemple d'exécution:
~$ free -m
total used free shared buff/cache available
Mem: 15050 5427 3690 56 5931 4803
Swap: 0 0 0
~$ sudo qemu-system-x86_64 -m 10240 # and other options
qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory
~$ echo 3 | sudo tee /proc/sys/vm/drop_caches
3
~$ free -m
total used free shared buff/cache available
Mem: 15050 1799 9446 56 3803 9414
Swap: 0 0 0
~$ sudo qemu-system-x86_64 -m 10240 # and other options
qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory
~$ echo 3 | sudo tee /proc/sys/vm/drop_caches
3
~$ free -m
total used free shared buff/cache available
Mem: 15050 1502 10819 56 2727 10784
Swap: 0 0 0
~$ sudo qemu-system-x86_64 -m 10240 # and other options
# Now QEMU starts