On Thu, Aug 29, 2013 at 2:09 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > [+cc linux-kernel, since more folks might be interested] > I don't know what the BIOS "auto" setting means, but it must mean > something in case 3, because that's the only case where OS support is > required. But if the OS is smart enough to manage MPS for hot-added > devices, why can't the OS also program MPS for the whole system at > boot-time? > > That's why I don't understand what BIOS wants to do. It sounds like > they want the performance benefit of larger MPS for devices present in > hot-plug slots at boot-time, even if the OS doesn't actively manage > MPS and things blow up if that device is replaced with one that > supports a smaller MPS. That choice doesn't make sense. > > In case 3, with a non-MPS-aware OS, you get better performance for a > while, but blow up if a card is replaced. And with an MPS-aware OS, > there should be no advantage to case 3: the OS should be able to get > good performance by programming MPS itself, even without help from the > BIOS. With OS default setting on case 3, other two OS are ok with hotplug, but Linux does not. Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
