On 3/10/2018 12:37 AM, Hyong Youb Kim wrote: > On Fri, Mar 09, 2018 at 03:57:46PM +0000, Ferruh Yigit wrote: >> On 3/9/2018 3:51 PM, Ananyev, Konstantin wrote: > [...] >>>> Is this work based on an application that uses max_rx_pkt_len and to make >>>> PMD >>>> compatible with that application? If so we can continue with patch, but if >>>> the >>>> patch is to implement DPDK properly I suggest postponing this until >>>> max_rx_pkt_len clarified. >>>> >>>> [1] >>>> https://dpdk.org/ml/archives/dev/2018-March/092178.html >>> >>> I think there are quite a lot apps these days that might rely on setting >>> MTU via >>> rxmode.max_rx_pkt_len. >>> I think we need to support them till we (ever) deprecate >>> rxmode.max_rx_pkt_len. >> >> Right. I was trying to save effort in case something changes related >> max_rx_pkt_len, but since it is not clear yet, will continue with this patch. >> >>> Konstantin >>> > > testpmd has a command to change max_rx_pkt_len, a few DTS test cases > rely on this feature to see if packets of certain sizes get dropped, > and so on. We worked on this patch to support these cases. > > I prefer using only MTU, to follow the convention of most (all?) > OSes. Though, this feature (max_rx_pkt_len) seems to come straight > from an Intel 82599 feature. In its datasheet, see "8.2.3.22.13 Max > Frame Size -- MAXFRS". Like to understand use cases for that, if > anyone can share.
ixgbe driver updates MAXFRS register in ixgbe_dev_mtu_set(), so mtu seems can replace max_rx_pkt_len. MAXFRS is for rx only, from datasheet description of it: "This value has no effect on transmit frames; it is the responsibility of software to limit the size of transmit frames" This may be the reason a new variable has been created for rx_frames, to differentiate it from mtu. Not sure if max rx and tx size can be different values for ixgbe. > > -Hyong >
