2014-08-20 09:16+0200, Paolo Bonzini: > Il 19/08/2014 22:35, Radim Krčmář ha scritto: > > Every increase of ple_window_grow creates potential overflows. > > They are not serious, because we clamp ple_window and userspace is > > expected to fix ple_window_max within a second. > > --- > I think avoiding overflows is better. In fact, I think you should call > this function for ple_window_max too. (Ack, I just wanted to avoid the worst userspace error, which is why PW_max hasn't changed when PW_grow got smaller and we could overflow.) > You could keep the ple_window_max variable to the user-set value. > Whenever ple_window_grow or ple_window_max are changed, you can set an > internal variable (let's call it ple_window_actual_max, but I'm not wed > to this name) to the computed value, and then do: > > if (ple_window_grow < 1 || ple_window_actual_max < ple_window) > new = ple_window; > else if (ple_window_grow < ple_window) > new = max(ple_window_actual_max, old) * ple_window_grow; > else > new = max(ple_window_actual_max, old) + ple_window_grow; Oh, I like that this can get rid of all overflows, ple_window_actual_max (PW_effective_max?) is going to be set to "ple_window_max [/-] ple_window_grow" in v2. > (I think the || in the first "if" can be eliminated with some creativity > in clamp_ple_window_max). To do it, we'll want to intercept changes to ple_window as well. (I disliked this patch a lot even before :) -- 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
