On 04/23/2012 06:27 PM, Richard Davies wrote: > We run a number of relatively large x86-64 hosts with twenty or so qemu-kvm > virtual machines on each of them, and I'm have some trouble with over-eager > swapping on some of the machines. This is resulting in load spikes during the > swapping and customer reports of very poor response latency from the virtual > machines which have been swapped out, despite the hosts apparently having > large amounts of free memory, and running fine if swap is turned off. > > > All of the hosts are currently running a 3.1.4 or 3.2.2 kernel and have ksm > enabled with 64GB of RAM and 2x eight-core AMD Opteron 6128 processors. > However, we have seen this same problem since 2010 on a 2.6.32.7 kernel and > older hardware - see http://marc.info/?l=linux-mm&m=128075337008943 > (previous helpful contributors cc:ed here - thanks). > > We have /proc/sys/vm/swappiness set to 0. The kernel config is here: > http://users.org.uk/config-3.1.4 Although you set swappiness to 0, kernel can swap out anon pages in current implementation. I think it's a severe problem. Couldn't this patch help you? http://permalink.gmane.org/gmane.linux.kernel.mm/74824 It can prevent anon pages's swap out until few page cache remain. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>