On Thu, 7 Sep 2023 07:16:50 +0000 Hayes Wang wrote: > > Before we tweak the heuristics let's make sure rx_bottom() behaves > > correctly. Could you make sure that > > - we don't perform _any_ rx processing when budget is 0 > > (see the NAPI documentation under Documentation/networking) > > The work_done would be 0, and napi_complete_done() wouldn't be called. > However, skb_queue_len(&tp->rx_queue) may be increased. I think it is > not acceptable, right? If budget is 0 we got called by netconsole, meaning we may be holding arbitrary locks. And we can't use napi_alloc_skb() which is for softirq/bh context only. We should only try to complete Tx in that case, since r8152_poll() doesn't handle any Tx the right thing seems to be to add if (!budget) return 0; > > - finish the current aggregate even if budget run out, return > > work_done = budget in that case. > > With this change the rx_queue thing should be gone completely. > > Excuse me. I don't understand this part. I know that when the packets are > more than budget, the maximum packets which could be handled is budget. > That is, return work_done = budget. However, the extra packets would be queued > to rx_queue. I don't understand what you mean about " the rx_queue thing > should be gone completely". I think the current driver would return > work_done = budget, and queue the other packets. I don't sure what you > want me to change. Nothing will explode if we process a few more packets than budget (assuming budget > 0). If we already do allocations and prepare those skbs - there's no point holding onto them in the driver. Just sent them up the stack (and then we won't need the local rx_queue). > > - instead of copying the head use napi_get_frags() + napi_gro_frags() > > it gives you an skb, you just attach the page to it as a frag and > > hand it back to GRO. This makes sure you never pull data into head > > rather than just headers. > > I would study about them. Thanks. > > Should I include above changes for this patch? > I think I have to submit another patches for above. > > > Please share the performance results with those changes. > > I couldn't reproduce the problem, so I couldn't provide the result > with the differences. Hm, if you can't repro my intuition would be to only take the patch for budget=0 handling into net, and the rest as improvements into net-next.
