> >>> I have no preference. Just curious, especially if it complicates the patch. > >>> > >> My understanding is that. It's probably ok for net. But we probably need > >> to document the assumptions to make sure it was not abused in other drivers. > >> > >> Introduce new parameters for find_vqs() can help to eliminate the subtle > >> stuffs but I agree it looks like a overkill. > >> > >> (Btw, I forget the numbers but wonder how much difference if we simple > >> remove the free_old_xmits() from the rx NAPI path?) > > The committed patchset did not record those numbers, but I found them > > in an earlier iteration: > > > > [PATCH net-next 0/3] virtio-net tx napi > > https://lists.openwall.net/netdev/2017/04/02/55 > > > > It did seem to significantly reduce compute cycles ("Gcyc") at the > > time. For instance: > > > > TCP_RR Latency (us): > > 1x: > > p50 24 24 21 > > p99 27 27 27 > > Gcycles 299 432 308 > > > > I'm concerned that removing it now may cause a regression report in a > > few months. That is higher risk than the spurious interrupt warning > > that was only reported after years of use. > > > Right. > > So if Michael is fine with this approach, I'm ok with it. But we > probably need to a TODO to invent the interrupt handlers that can be > used for more than one virtqueues. When MSI-X is enabled, the interrupt > handler (vring_interrup()) assumes the interrupt is used by a single > virtqueue. Thanks. The approach to schedule tx-napi from virtnet_poll_cleantx instead of cleaning directly in this rx-napi function was not effective at suppressing the warning, I understand. It should be easy to drop the spurious rate to a little under 99% percent, if only to suppress the warning. By probabilistically cleaning in virtnet_poll_cleantx only every 98/100, say. But that really is a hack. There does seem to be a huge potential for cycle savings if we can really avoid the many spurious interrupts. As scheduling napi_tx from virtnet_poll_cleantx is not effective, agreed that we should probably look at the more complete solution to handle both tx and rx virtqueues from the same IRQ. And revert this explicit warning suppression patch once we have that. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
