On Wed, May 28, 2025 at 8:45 AM Stanislav Fomichev <stfomichev@xxxxxxxxx> wrote: > > On 05/28, Dragos Tatulea wrote: > > On Tue, May 27, 2025 at 09:05:49AM -0700, Stanislav Fomichev wrote: > > > On 05/23, Tariq Toukan wrote: > > > > This series from the team adds support for zerocopy rx TCP with devmem > > > > and io_uring for ConnectX7 NICs and above. For performance reasons and > > > > simplicity HW-GRO will also be turned on when header-data split mode is > > > > on. > > > > > > > > Find more details below. > > > > > > > > Regards, > > > > Tariq > > > > > > > > Performance > > > > =========== > > > > > > > > Test setup: > > > > > > > > * CPU: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz (single NUMA) > > > > * NIC: ConnectX7 > > > > * Benchmarking tool: kperf [1] > > > > * Single TCP flow > > > > * Test duration: 60s > > > > > > > > With application thread and interrupts pinned to the *same* core: > > > > > > > > |------+-----------+----------| > > > > | MTU | epoll | io_uring | > > > > |------+-----------+----------| > > > > | 1500 | 61.6 Gbps | 114 Gbps | > > > > | 4096 | 69.3 Gbps | 151 Gbps | > > > > | 9000 | 67.8 Gbps | 187 Gbps | > > > > |------+-----------+----------| > > > > > > > > The CPU usage for io_uring is 95%. > > > > > > > > Reproduction steps for io_uring: > > > > > > > > server --no-daemon -a 2001:db8::1 --no-memcmp --iou --iou_sendzc \ > > > > --iou_zcrx --iou_dev_name eth2 --iou_zcrx_queue_id 2 > > > > > > > > server --no-daemon -a 2001:db8::2 --no-memcmp --iou --iou_sendzc > > > > > > > > client --src 2001:db8::2 --dst 2001:db8::1 \ > > > > --msg-zerocopy -t 60 --cpu-min=2 --cpu-max=2 > > > > > > > > Patch overview: > > > > ================ > > > > > > > > First, a netmem API for skb_can_coalesce is added to the core to be able > > > > to do skb fragment coalescing on netmems. > > > > > > > > The next patches introduce some cleanups in the internal SHAMPO code and > > > > improvements to hw gro capability checks in FW. > > > > > > > > A separate page_pool is introduced for headers. Ethtool stats are added > > > > as well. > > > > > > > > Then the driver is converted to use the netmem API and to allow support > > > > for unreadable netmem page pool. > > > > > > > > The queue management ops are implemented. > > > > > > > > Finally, the tcp-data-split ring parameter is exposed. > > > > > > > > Changelog > > > > ========= > > > > > > > > Changes from v1 [0]: > > > > - Added support for skb_can_coalesce_netmem(). > > > > - Avoid netmem_to_page() casts in the driver. > > > > - Fixed code to abide 80 char limit with some exceptions to avoid > > > > code churn. > > > > > > Since there is gonna be 2-3 weeks of closed net-next, can you > > > also add a patch for the tx side? It should be trivial (skip dma unmap > > > for niovs in tx completions plus netdev->netmem_tx=1). > > > > > Seems indeed trivial. We will add it. > > > > > And, btw, what about the issue that Cosmin raised in [0]? Is it addressed > > > in this series? > > > > > > 0: https://lore.kernel.org/netdev/9322c3c4826ed1072ddc9a2103cc641060665864.camel@xxxxxxxxxx/ > > We wanted to fix this afterwards as it needs to change a more subtle > > part in the code that replenishes pages. This needs more thinking and > > testing. > > Thanks! For my understanding: does the issue occur only during initial > queue refill? Or the same problem will happen any time there is a burst > of traffic that might exhaust all rx descriptors? > Minor: a burst in traffic likely won't reproduce this case, I'm sure mlx5 can drive the hardware to line rate consistently. It's more if the machine is under extreme memory pressure, I think, page_pool_alloc_pages and friends may return ENOMEM, which reproduces the same edge case as the dma-buf being extremely small which also makes page_pool_alloc_netmems return -ENOMEM. -- Thanks, Mina
