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The comparison is traffic received on ifn3 and transmit ifn4 to traffic rec= eived on ifn3, ifn5 and transmit on ifn4, ifn6. When transmit packets on one port the performance is better, however when t= ransmit on two ports the performance across the two drops dramatically. There is increase of 55.29% of the CPU spent in common_ring_mp_enqueue and = 54.18% less time in i40e_xmit_pkts (was E810 tried x710). The common_ring_mp_enqueue is multi-producer, is the enqueue of mbuf point= ers passed in to rte_eth_tx_burst() have to be multi-producer? Is there a way to change dpdk to use single-producer? # Event 'cycles' # # Baseline Delta Abs Shared Object Symbol # ........ ......... ................. .................................= ..... # 36.37% +55.29% test [.] common_ring_mp_enque= ue 62.36% -54.18% test [.] i40e_xmit_pkts 1.10% -0.94% test [.] dpdk_tx_thread 0.01% -0.01% [kernel.kallsyms] [k] native_sched_clock +0.00% [kernel.kallsyms] [k] fill_pmd +0.00% [kernel.kallsyms] [k] perf_sample_event_too= k 0.00% +0.00% [kernel.kallsyms] [k] __flush_smp_call_function_q= ueue 0.02% [kernel.kallsyms] [k] __intel_pmu_enable_a= ll.constprop.0 0.02% [kernel.kallsyms] [k] native_irq_return_ir= et 0.02% [kernel.kallsyms] [k] native_tss_update_io= _bitmap 0.01% [kernel.kallsyms] [k] ktime_get 0.01% [kernel.kallsyms] [k] perf_adjust_freq_unt= hr_context 0.01% [kernel.kallsyms] [k] __update_blocked_fai= r 0.01% [kernel.kallsyms] [k] perf_adjust_freq_unt= hr_events Thanks, Ed -----Original Message----- From: Lombardo, Ed=20 Sent: Sunday, July 6, 2025 1:45 PM To: Stephen Hemminger Cc: Ivan Malov ; users Subject: RE: dpdk Tx falling short Hi Stephen, If using dpdk rings comes with this penalty then what should I use, is ther= e an alterative to rings. We do not want to use shared memory and do buffe= r copies? Thanks, Ed -----Original Message----- From: Stephen Hemminger =20 Sent: Sunday, July 6, 2025 12:03 PM To: Lombardo, Ed Cc: Ivan Malov ; users Subject: Re: dpdk Tx falling short External Email: This message originated outside of NETSCOUT. Do not click l= inks or open attachments unless you recognize the sender and know the conte= nt is safe. On Sun, 6 Jul 2025 00:03:16 +0000 "Lombardo, Ed" wrote: > Hi Stephen, > Here are comments to the list of obvious causes of cache misses you menti= ond. >=20 > Obvious cache misses. > - passing packets to worker with ring - we use lots of rings to pass mbu= f pointers. If I skip the rte_eth_tx_burst() and just free mbuf bulk, the = tx ring does not fill up. > - using spinlocks (cost 16ns) - The driver does not use spinlocks, othe= r than what dpdk uses. > - fetching TSC - We don't do this, we let Rx offload timestamp packets. > - syscalls? - No syscalls are done in our driver fast path. >=20 > You mention "passing packets to worker with ring", do you mean using ring= s to pass mbuf pointers causes cache misses and should be avoided? Rings do cause data to be modified by one core and examined by another so t= hey are a cache miss.