I think I found my answer in the "Understanding Memory Resource Management" guide here: http://www.vmware.com/files/pdf/mem_mgmt_perf_vsphere5.pdf Section "When to Reclaim Host Memory" page 15...
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I think I found my answer in the "Understanding Memory Resource Management" guide here: http://www.vmware.com/files/pdf/mem_mgmt_perf_vsphere5.pdf Section "When to Reclaim Host Memory" page 15: "In the high state, the aggregate virtual machine guest memory usage is smaller than the host memory size. Whether or not host memory is overcommitted, the hypervisor will not reclaim memory through ballooning or swapping. (This is true only when the virtual machine memory limit is not set.) If host free memory drops towards the soft threshold, the hypervisor starts to reclaim memory using ballooning. Ballooning happens before free memory actually reaches the soft threshold because it takes time for the balloon driver to allocate and pin guest physical memory. Usually, the balloon driver is able to reclaim memory in a timely fashion so that the host free memory stays above the soft threshold." I checked esxtop, pressing "m" for memory view, and I can see that the hosts VMKMEM shows "high state", so the only way memory is currently reclaimed is by page sharing. Only when I start to run out of host memory, this state changes to "soft" or "hard", will ballooning or swapping take place to free up the guest "free" memory. esxtop show my "minfree" as 940 MB, while it shows that I have 6960MB of free physically memory.
