在 2024/12/3 20:39, Uladzislau Rezki 写道:
On Tue, Dec 03, 2024 at 07:23:44PM +0800, zuoze wrote:We have implemented host-guest communication based on the TUN device using XSK[1]. The hardware is a Kunpeng 920 machine (ARM architecture), and the operating system is based on the 6.6 LTS version with kernel version 6.6. The specific stack for hotspot collection is as follows: - 100.00% 0.00% vhost-12384 [unknown] [k] 0000000000000000 - ret_from_fork - 99.99% vhost_task_fn - 99.98% 0xffffdc59f619876c - 98.99% handle_rx_kick - 98.94% handle_rx - 94.92% tun_recvmsg - 94.76% tun_do_read - 94.62% tun_put_user_xdp_zc - 63.53% __check_object_size - 63.49% __check_object_size.part.0 find_vmap_area - 30.02% _copy_to_iter __arch_copy_to_user - 2.27% get_rx_bufs - 2.12% vhost_get_vq_desc 1.49% __arch_copy_from_user - 0.89% peek_head_len 0.54% xsk_tx_peek_desc - 0.68% vhost_add_used_and_signal_n - 0.53% eventfd_signal eventfd_signal_mask - 0.94% handle_tx_kick - 0.94% handle_tx - handle_tx_copy - 0.59% vhost_tx_batch.constprop.0 0.52% tun_sendmsg It can be observed that most of the overhead is concentrated in the find_vmap_area function.I see. Yes, it is pretty contented, since you run the v6.6 kernel. There was a work that tends to improve it to mitigate a vmap lock contention. See it here: https://lwn.net/Articles/956590/ The work was taken in the v6.9 kernel: <snip> commit 38f6b9af04c4b79f81b3c2a0f76d1de94b78d7bc Author: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Date: Tue Jan 2 19:46:23 2024 +0100 mm: vmalloc: add va_alloc() helper Patch series "Mitigate a vmap lock contention", v3. 1. Motivation ... <snip> Could you please try the v6.9 kernel on your setup? How to solve it, probably, it can be back-ported to the v6.6 kernel.
All the vmalloc-related optimizations have already been merged into 6.6, including the set of optimization patches you suggested. Thank you very much for your input.
Thanks! -- Uladzislau Rezki
Thanks, ze zuo
