[Bug 2107347] Re: Severe Network Performance Regression with BCM57800/BCM57810 on Kernel 6.8.0-40 through 6.12.16

All 3 presented the issue

Linux srv1r730xd-007d 6.7.6-060706-generic #519475c5 SMP PREEMPT_DYNAMIC Wed Jul 2 09:22:01 CEST 2025 x86_64 x86_64 x86_64 GNU/Linux
2025-07-02 15:25:31 (247 MB/s)

Linux srv1r730xd-007d 6.7.6-060706-generic #cfc86a96 SMP PREEMPT_DYNAMIC Wed Jul 2 12:44:36 CEST 2025 x86_64 x86_64 x86_64 GNU/Linux
2025-07-02 15:36:30 (245 MB/s)

Linux srv1r730xd-007d 6.7.6-060706-generic #fa658e37 SMP PREEMPT_DYNAMIC Wed Jul 2 10:33:41 CEST 2025 x86_64 x86_64 x86_64 GNU/Linux
2025-07-02 15:50:27 (230 MB/s)

And just to confirm I tried again with the kernel from post #37

Linux srv1r730xd-007d 6.7.6-lp2107347s08-generic #202506091846 SMP PREEMPT_DYNAMIC Mon Jun 9 17:20:08 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
2025-07-02 15:58:19 (331 MB/s)

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Title:
Severe Network Performance Regression with BCM57800/BCM57810 on Kernel
6.8.0-40 through 6.12.16

Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Jammy:
In Progress

Bug description:
Significant network performance degradation when using Broadcom
BCM57800/BCM57810 (bnx2x) NICs with jumbo frames on Ubuntu Jammy with
kernels starting from 6.8.0-38, with the issue becoming severe and
rendering the system unusable from 6.8.0-40 onwards.

There is a similar report here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2098961
However, the proposed fix in that report does not resolve the issue for BCM57800 using the bnx2x driver.

Environment:
OS: Ubuntu 22.04(Jammy Jellyfish)
Current HWE Kernel: 6.8.0-57.59~22.04.1
NIC: Broadcom BCM57800 / BCM57810
Driver: bnx2x

Observed Behavior:
Noticeable network degradation begins in kernel 6.8.0-38
Becomes unusable in kernel 6.8.0-40 and beyond
Still reproducible in latest HWE kernel 6.8.0-57
Lowering the MTU to 1500 increases performance

Expected Behavior:
Stable and performant network performance as seen in previous kernel versions

Additional Notes: As mentioned in LP#2098961, the issue appears to be
fixed in kernel 6.12.17[0].

Request that this fix be backported or that further investigation be
made into kernel regressions affecting bnx2x on these NICs.

[0] https://kernel.ubuntu.com/mainline/v6.12.17/

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