<snip> > > > > Hi Jakub, > > I am trying to review this patch. I am having difficulty in > > understanding the implementation for the queue/ring, appreciate if you > > could help me understand the logic. > > 'ring' refers to a ring buffer holding packet descriptors. These descriptors > hold metadata about the packet (packet buffer address, length, etc..). > 'queues' are a representation of rings and buffers (+ some metadata). In > more detail, one ring (S2M) and packet buffers allocated for this ring would > be represented as 'tx queue' for the slave and 'rx queue' for the master. Thanks Jakub. I could run the testpmd app and was able to understand the implementation. I found some issues and I have sent out a patch series [1].
[1] https://patches.dpdk.org/patch/78212/ > > > > > 1) The S2M queues - are used to send packets from slave to master. My > > understanding is that, the slave thread would call 'eth_memif_tx_zc' > > and the master thread would call 'eth_memif_rx_zc'. Is this correct? > > 2) The M2S queues - are used to send packets from master to slave. > > Here the slave thread would call 'eth_memif_rx_zc' and the master > > thread would call 'eth_memif_tx_zc'. Is this correct? > > This is inded correct. > > > > > Thank you, > > Honnappa > > > > > -----Original Message----- > > > From: Phil Yang <phil.y...@arm.com> > > > Sent: Friday, September 11, 2020 12:38 AM > > > To: jgraj...@cisco.com; dev@dpdk.org > > > Cc: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>; Ruifeng > > > Wang <ruifeng.w...@arm.com>; nd <n...@arm.com> > > > Subject: [PATCH] net/memif: relax barrier for zero copy path > > > > > > Using 'rte_mb' to synchronize the shared ring head/tail between > > > producer and consumer will stall the pipeline and damage performance > > > on the weak memory model platforms, such like aarch64. > > > > > > Relax the expensive barrier with c11 atomic with explicit memory > > > ordering can improve 3.6% performance on throughput. > > My question here is: `rte_mb` is supposed to make sure that head/tail > pointer are not updated before the packets are written into shared memory. > Does the atomic ensures that the packets are written into shared memory > before head/tail pointers are updated?