Olá,
meu servidor de email aqui (debian, exim4, qpopper, procmail, spamassassin) as vezes pára de responder... derruba as conexões ssh, não responde via http.... ou seja.. pára tudo... mas continua PINGando...

localmente fica exibindo a seguinte mensagem na tela repetidamente:

Apr 4 16:05:48 omega kernel: VM: killing process in.qpopper
Apr 4 16:05:48 omega kernel: __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
Apr 4 16:05:48 omega last message repeated 5 times
Apr 4 16:05:48 omega kernel: VM: killing process apache2
Apr 4 16:05:48 omega kernel: __alloc_pages: 0-order allocation failed (gfp=0x1f0/0)
Apr 4 16:05:49 omega kernel: __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
Apr 4 16:05:49 omega kernel: VM: killing process exim4
Apr 4 16:05:49 omega kernel: __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
Apr 4 16:05:49 omega kernel: VM: killing process spamassassin
o que seria isso?
como arrumar?