NACK: [PATCH 1/1][SRU][B][E][F][G][Unstable] UBUNTU: SAUCE: e1000e: Disable TSO for buffer overrun workaround

[Stefan Bader]

On 13.05.20 10:58, AceLan Kao wrote:
> From: Kai-Heng Feng <kai.heng.feng at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1802691
> 
> Commit b10effb92e27 ("e1000e: fix buffer overrun while the I219 is
> processing DMA transactions") imposes roughly 30% performance penalty.
> 
> The commit log states that "Disabling TSO eliminates performance loss
> for TCP traffic without a noticeable impact on CPU performance", so
> let's disable TSO by default to regain the loss.
> 
> Fixes: b10effb92e27 ("e1000e: fix buffer overrun while the I219 is processing DMA transactions")
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
> (cherry picked from commit https://lkml.org/lkml/2020/5/7/676)
> Signed-off-by: AceLan Kao <acelan.kao at canonical.com>
> ---

Disabling segmentation offload does not sound like a proper fix to the problem.
Even if you do not notice anything on your CPU that might be different in other
scenarios. And this does not seem to have any response upstream on the mailing list.

>  drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index cfbdcf4838a7..6e85032d8916 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -5293,6 +5293,10 @@ static void e1000_watchdog_task(struct work_struct *work)
>  					/* oops */
>  					break;
>  				}
> +				if (hw->mac.type == e1000_pch_spt) {
> +					netdev->features &= ~NETIF_F_TSO;
> +					netdev->features &= ~NETIF_F_TSO6;
> +				}
>  			}
>  
>  			/* enable transmits in the hardware, need to do this
> 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <https://lists.ubuntu.com/archives/kernel-team/attachments/20200513/eeadd295/attachment.sig>