* Alexander Graf <agraf@xxxxxxx> wrote: > So the simple rule is: don't register a coalesced MMIO region for a > region where latency matters. [...] So my first suspicion is confirmed. A quick look at Qemu sources shows that lots of drivers are using coalesced_mmio without being aware of the latency effects and only one seems to make use of qemu_flush_coalesced_mmio_buffer(). Drivers like hw/e1000.c sure look latency critical to me. So i maintain my initial opinion: this is a pretty dangerous 'optimization' that should be used with extreme care: i can tell it you with pretty good authority that latency problems are much more easy to introduce than to find and remove ... Thanks, Ingo -- 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
