On 2024/12/3 21:51, Uladzislau Rezki wrote:
On Tue, Dec 03, 2024 at 09:45:09PM +0800, Kefeng Wang wrote:
On 2024/12/3 21:39, Uladzislau Rezki wrote:
On Tue, Dec 03, 2024 at 09:30:09PM +0800, Kefeng Wang wrote:
On 2024/12/3 21:10, zuoze wrote:
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.
...
Thank you. Then you have tons of copy_to_iter/copy_from_iter calls
during your test case. Per each you need to find an area which might
be really heavy.
Exactly, no vmalloc check before 0aef499f3172 （"mm/usercopy: Detect
vmalloc overruns"), so no burden in find_vmap_area in old kernel.
How many CPUs in a system you have?
128 core
