On 14 Aug 2013, at 15:26, Kaveh Razavi wrote: > This is a good idea, since it relaxes the requirement for releasing the > cache only on shutdown. I am not sure how the 'finish point' can be > recognized. Full cache quota is one obvious scenario, but I imagine most > VMs do/should not really read till that point (unless they are doing > something that should not be cached anyway - e.g. file-system check). > Another possibility is registering some sort of event to be executed > periodically (e.g. every 30 seconds), and if the cache is not modified > in a period, then that is the 'finish point'. I do not know how feasible > that is with the facilities that qemu provides.
You can set timers and modify them - that's easy enough. I suspect the heuristic may need some tuning, but a simple one such as '60 seconds after boot' might be sufficient. After all, if a VM takes more than 60 seconds to boot and does not fill the cache quota in that time, I think we can assume the cache isn't going to do it much good! -- Alex Bligh
