On 10/15/2014 06:25 PM, Michael S. Tsirkin wrote: > On Wed, Oct 15, 2014 at 03:25:24PM +0800, Jason Wang wrote: >> According to David, proper accounting and queueing (at all levels, not >> just TCP sockets) is more important than trying to skim a bunch of >> cycles by avoiding TX interrupts. > He also mentioned we should find other ways to batch > Right. >> Having an event to free the SKB is >> absolutely essential for the stack to operate correctly. >> >> This series tries to enable tx interrupt for virtio-net. The idea is >> simple: enable tx interrupt and schedule a tx napi to free old xmit >> skbs. >> >> Several notes: >> - Tx interrupt storm avoidance when queue is about to be full is >> kept. > But queue is typically *not* full. More important to avoid interrupt > storms in that case IMO. Yes. >> Since we may enable callbacks in both ndo_start_xmit() and tx >> napi, patch 1 adds a check to make sure used event never go >> back. This will let the napi not enable the callbacks wrongly after >> delayed callbacks was used. > So why not just use delayed callbacks? This means the tx interrupt are coalesced in a somewhat adaptive way. Need benchmark to see its effect. > >> - For bulk dequeuing, there's no need to enable tx interrupt for each >> packet. The last patch only enable tx interrupt for the final skb in >> the chain through xmit_more and a new helper to publish current avail >> idx as used event. >> >> This series fixes several issues of original rfc pointed out by Michael. > Could you list the issues, for ease of review? Probably just one: - Move the virtqueue_disable_cb() from skb_xmit_done() into virtnet_poll_tx() under tx lock. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
