Hi all, While measuring the impact of a kernel patch on our lab machines I stumbled upon a performance regression affecting the 100Gbit ICE nic and bisected it from range v5.11.1..v5.13-rc3 to the commit: a250c23f15c2 iommu: remove DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE Both recent bpf-next (d6a6a55518) and linux-stable (c4681547bc) are affected by the issue. The regression shows as a significant drop in throughput as measured with "super_netperf" [0], with measured bandwidth of ~95Gbps before and ~35Gbps after: commit 3189713a1b84 (a250c23^): $ ./super_netperf 32 -H 172.18.0.2 -l 10 97379.8 commit a250c23f15c2: $ ./super_netperf 32 -H 172.18.0.2 -l 10 34097.5 The pair of test machines have this hardware: CPU: AMD Ryzen 9 3950X 16-Core Processor MB: X570 AORUS MASTER 0a:00.0 Ethernet controller [0200]: Intel Corporation Ethernet Controller E810-C for QSFP [8086:1592] (rev 02) Kernel config: https://gist.github.com/joamaki/9ee11294c78a8dd2776041f67e5620e7 [0] https://github.com/borkmann/stuff/blob/master/super_netperf
