On Mon, 21 Oct 2024 02:00:55 +0000 Chaoyong He <chaoyong...@corigine.com> wrote:
> > On Fri, 18 Oct 2024 05:50:20 +0000 > > Chaoyong He <chaoyong...@corigine.com> wrote: > > > > > > On Fri, 18 Oct 2024 03:21:28 +0000 > > > > Chaoyong He <chaoyong...@corigine.com> wrote: > > > > > > > > > > RTE_PKTMBUF_HEADROOM); } > > > > > > > + > > > > > > > > > > > > Not sure why this is needed? What is the problem with the original > > code? > > > > > > Are you trying to force packets to be segmented? > > > > > > > > > > Actually, we are trying to force packets *not* segmented by making > > > > > the > > > > mbuf size large enough to hold the packets. > > > > > > > > > > In our user case, we start l3fwd app with parameter '--max-pkt-len > > > > > 4000', > > > > and obviously the original logic with RTE_MBUF_DEFAULT_DATAROOM > > mbuf > > > > size will cause the packets to be segmented. > > > > > Which is not what we want, so we add this new '--mbuf-size=4096' > > > > parameter, the mbuf size will large enough to hold even the largest > > > > packet. > > > > > > > > > > Do you think this make sense? > > > > > > > > Maybe query the driver, and use the max_rx_pkt_len as input to > > > > deciding the right mbuf size. > > > > > > Sorry, I am not quite understanding here. > > > I can't find 'max_rx_pkt_len' in l3fwd app, instead it's exist testpmd > > > app. > > > Could you please explain a little more about the advice? > > > > In rte_eth_dev_info, I meant the field max_rx_bufsize and there is also > > max_rx_pktlen. > > > > > > > > > If max-pkt-len was 4000 and driver can only take 2K buffers, then > > > > use 2K mbuf size. > > > > If max-pkt-len was 1500 then use mtu + headroom and round up > > Oh, I understand what you mean now, thanks for the clarification. > But the solution you suppose is not flexible enough, thus can't satisfy our > needs. > > Follow your example and consider this situation: > If max-pkt-len was 4000 and driver can only take 2K buffers, then > use 2K mbuf size. > > But we want to measure the performance when the mbuf size is 1024 and 512. > > Then there is no way to do this in your solution, I suppose? > > But with our '--mbuf-size' parameter, we can easily do that. > Thanks for your hint, we realized our solution also has a little problem, > which not > consider the 'max_rx_bufsize' of rte_eth_dev_info, and we will fix that in > the next version patch. It would be best if the default was to choose mbuf size automatically, but since this is a test program having an override is also useful. In general l3fwd is target at usability (less options) and test-pmd is focused on testing (lots of options). There is a tradeoff here. l3fwd should not get as complex as test-pmd or there is no point.
