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In this patch, we add dcbnl buffer attribute to allow user change the NIC's buffer configuration such as priority to buffer mapping and buffer size of individual buffer. This attribute combined with pfc attribute allows advanced user to fine tune the qos setting for specific priority queue. For example, user can give dedicated buffer for one or more priorities or user can give large buffer to certain priorities. The dcb buffer configuration will be controlled by lldptool. lldptool -T -i eth2 -V BUFFER prio 0,2,5,7,1,2,3,6 maps priorities 0,1,2,3,4,5,6,7 to receive buffer 0,2,5,7,1,2,3,6 lldptool -T -i eth2 -V BUFFER size 87296,87296,0,87296,0,0,0,0 sets receive buffer size for buffer 0,1,2,3,4,5,6,7 respectively After discussion on mailing list with Jakub, Jiri, Ido and John, we agreed to choose dcbnl over devlink interface since this feature is intended to set port attributes which are governed by the netdev instance of that port, where devlink API is more suitable for global ASIC configurations. We present an use case scenario where dcbnl buffer attribute configured by advance user helps reduce the latency of messages of different sizes. Scenarios description: On ConnectX-5, we run latency sensitive traffic with small/medium message sizes ranging from 64B to 256KB and bandwidth sensitive traffic with large messages sizes 512KB and 1MB. We group small, medium, and large message sizes to their own pfc enables priorities as follow. Priorities 1 & 2 (64B, 256B and 1KB) Priorities 3 & 4 (4KB, 8KB, 16KB, 64KB, 128KB and 256KB) Priorities 5 & 6 (512KB and 1MB) By default, ConnectX-5 maps all pfc enabled priorities to a single lossless fixed buffer size of 50% of total available buffer space. The other 50% is assigned to lossy buffer. Using dcbnl buffer attribute, we create three equal size lossless buffers. Each buffer has 25% of total available buffer space. Thus, the lossy buffer size reduces to 25%. Priority to lossless buffer mappings are set as follow. Priorities 1 & 2 on lossless buffer #1 Priorities 3 & 4 on lossless buffer #2 Priorities 5 & 6 on lossless buffer #3 We observe improvements in latency for small and medium message sizes as follows. Please note that the large message sizes bandwidth performance is reduced but the total bandwidth remains the same. 256B message size (42 % latency reduction) 4K message size (21% latency reduction) 64K message size (16% latency reduction) CC: Ido Schimmel <idosch@idosch.org> CC: Jakub Kicinski <jakub.kicinski@netronome.com> CC: Jiri Pirko <jiri@resnulli.us> CC: Or Gerlitz <gerlitz.or@gmail.com> CC: Parav Pandit <parav@mellanox.com> CC: Aron Silverton <aron.silverton@oracle.com> Signed-off-by: Huy Nguyen <huyn@mellanox.com> Reviewed-by: Parav Pandit <parav@mellanox.com> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com> |
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| .. | ||
| dcbevent.c | ||
| dcbnl.c | ||
| Kconfig | ||
| Makefile | ||