Adding netdev. On Wed, Feb 23, 2022 at 9:46 PM Harold Huang <[email protected]> wrote: > > Sorry. The performance tested by iperf is degraded from 4.5 Gbps to > 750Mbps per flow. > > Harold Huang <[email protected]> 于2022年2月23日周三 21:13写道： > > > > I see in dpdk virtio-user driver, the TUNSETSNDBUF is initialized with > > INT_MAX, see: > > https://github.com/DPDK/dpdk/blob/main/drivers/net/virtio/virtio_user/vhost_kernel_tap.c#L169
Note that Linux use INT_MAX as default sndbuf for tuntap. > > It is ok because tap driver uses it to support tx baching, see this > > patch: > > https://github.com/torvalds/linux/commit/0a0be13b8fe2cac11da2063fb03f0f39359b3069 > > > > But in tun_xdp_one, napi is not supported and I want to user napi in > > tun_get_user to enable gro. NAPI is not enabled in this path, want to send a patch to do that? Btw, NAPI mode is used for kernel networking stack hardening at start, but it would be interesting to see if it helps for the performance. > > As I result, I change the sndbuf to a > > value such as 212992 in /proc/sys/net/core/wmem_default. Can you describe your setup in detail? Where did you run the iperf server and client and where did you change the wmem_default? > > But the > > performance tested by iperf is greatly degraded, from 4.5 Gbps to > > 750Gbps per flow. I see the the iperf server consume 100% cpu core, > > which should be the bottleneck of the this test. The perf top result > > of iperf server cpu core is as follows: > > > > ''' > > Samples: 72 of event 'cycles', 4000 Hz, Event count (approx.): > > 22685278 lost: 0/0 drop: 0/0 > > Overhead Shared O Symbol > > 59.86% [kernel] [k] report_bug > > 20.66% [kernel] [k] module_find_bug > > 6.51% [kernel] [k] common_interrupt > > 2.82% [kernel] [k] __slab_free > > 1.48% [kernel] [k] copy_user_enhanced_fast_string > > 1.44% [kernel] [k] __skb_datagram_iter > > 1.42% [kernel] [k] notifier_call_chain > > 1.41% [kernel] [k] irq_work_run_list > > 1.41% [kernel] [k] update_irq_load_avg > > 1.41% [kernel] [k] task_tick_fair > > 1.41% [kernel] [k] cmp_ex_search > > 0.16% [kernel] [k] __ghes_peek_estatus.isra.12 > > 0.02% [kernel] [k] acpi_os_read_memory > > 0.00% [kernel] [k] native_apic_mem_write > > ''' > > I am not clear about the test result. Can we change the sndbuf size in > > dpdk? Is any way to enable vhost_net to use napi without changing the > > tun kernel driver? You can do this by not using INT_MAX as sndbuf. Thanks >
