* Anthony Liguori (anthony@xxxxxxxxxxxxx) wrote: > On 12/22/2009 06:02 PM, Chris Wright wrote: >> * Anthony Liguori (anthony@xxxxxxxxxxxxx) wrote: >>> The >>> virtio-net setup probably made extensive use of pinning and other tricks >>> to make things faster than a normal user would see them. It ends up >>> creating a perfect combination of batching which is pretty much just >>> cooking the mitigation schemes to do extremely well for one benchmark. >> >> Just pinning, the rest is stock virtio features like mergeable rx buffers, >> GRO, GSO (tx mitigation is actually disabled). > > Technically, tx mitigation isn't disabled. The heuristic is changed > such that instead of relying on a fixed timer, tx notification is > disabled until you can switch to another thread and process packets. > > The effect is that depending on time slice length and system load, you > adaptively enable tx mitigation. It's heavily dependent on the > particulars of the system and the overall load. > > For instance, this mitigation scheme looks great at high throughputs but > looks very bad at mid-to-low throughputs compared to timer based > mitigation (at least, when comparing CPU cost). Yep, you're right. thanks, -chris -- 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
