On 10/09/15 16:44, Laura Creighton wrote:
..., if your game engine is running on a server shared by other users and some of them are running critical apps (think a businesses billing or
We were talking about mobile devices ...
Ok, in that case I'd guess the client playing the game is only interested in the game so won't care about impact on other
processes.
These days every business billing and accounting suite I know of -- and we _make_ a bookkeeping suite, which we need to interface with many other things .... runs in its own VM and doesn't share with anybody.
But it does. The physical file system and its IO bus is still shared by every VM and therefore by every app on every VM. And when you do a flush you force the VM to write to the physical IO bus. Even if the VM uses a virtual file system (which is no good if you are sharing with other VMs in a common database environment) it will almost certainly be manifested as a physical file eventually. If you are lucky the VM will defer flushes to the physical FS but that is normally a configurable parameter. One of the biggest problems facing modern data centres is how to manage access to physical devices from virtual environments. It is a very delicate balancing act and very easy to get wrong. And where in the past a mistake upset a handful of apps it now impacts hundreds. We are still in early days with VM technology and the monitoring tools are improving and the hardware architectures are developing with parallel buses etc to avoid these kinds of problems. But most of the data centres I work with are still running at least 50% capacity on pre VM-optimised servers.
multiplayer games tend to run in their own VM as well, and too many users using the game can and does degrade performance. But I don't think that having too many users flush their stream objects is a significant part of this problem,
Regular flushes hardly ever affect the program doing the flushing. It's whatever is sharing the IO bus. Remember the issue is the physical hardware bus not the software environment. If you are writing to your own file system over a segregated bus (and there are several technologies for doing that (SAN, NAS, multiplexed buses etc etc)) then its not usually an issue. It's only if you are on a machine where you share a single IO channel with other apps that problems can occur - for the other apps. However, I suspect we might now be getting a wee bit OT for most readers on this list! So I will put my architect's hat away again. :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
