We're running KSM on kernel 2.6.39.2 with hosts running a number qemu-kvm virtual machines, and it has consistently been saving us a useful amount of RAM. To monitor the effective amount of memory saved, I've been looking at the difference between /sys/kernel/mm/ksm/pages_sharing and pages_shared. On a typical 32GB host, this has been coming out as at least a hundred thousand or so, which is presumably half to one gigabyte worth of 4k pages. However, this morning we've spotted something odd - a host where pages_sharing is smaller than pages_shared, giving a negative saving by the above calculation: # cat /sys/kernel/mm/ksm/pages_sharing 1099994 # cat /sys/kernel/mm/ksm/pages_shared 1761313 I think this means my interpretation of these values must be wrong, as I presumably can't have more pages being shared than instances of their use! Can anyone shed any light on what might be going on here for me? Am I misinterpreting these values, or does this look like it might be an accounting bug? (If the latter, what useful debug info can I extract from the system to help identify it?) Best wishes, Chris. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
