On Sat, 2010-08-28 at 15:58 +0200, Hans Verkuil wrote: > > Isn't the proposed CMA thing vulnerable to the exact same problem? If > > you allow sharing of regions and plug some allocator in there you get > > the same problem. If you can solve it there, you can solve it for any > > kind of reservation scheme. > > Since with cma you can assign a region exclusively to a driver you can ensure > that this problem does not occur. Of course, if you allow sharing then you will > end up with the same type of problem unless you know that there is only one > driver at a time that will use that memory. I think you could do the same thing, the proposed page allocator solutions still needs to manage pageblock state, you can manage those the same as you would your cma regions -- the difference is that you get the option of letting the rest of the system use the memory in a transparent manner if you don't need it. > There is obviously a trade-off. I was just wondering how costly it is. > E.g. would it be a noticeable delay making 64 MB memory available in this > way on a, say, 600 MHz ARM. Right, dunno really, rather depends on the memory bandwidth of your arm device I suspect. It is something you'd have to test. In case the machine isn't fast enough, there really isn't anything you can do but keep the memory empty at all times; unless of course the device in question needs it. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
