Re: [dpdk-dev] [PATCH] net/i40e: remove VF interrupt handler

["Xing, Beilei" <beilei.xing@intel.com>]

> -----Original Message-----
> From: Zhang, Qi Z
> Sent: Thursday, June 7, 2018 9:32 AM
> To: Xing, Beilei <beilei.xing@intel.com>
> Cc: Wu, Jingjing <jingjing.wu@intel.com>; Yu, De <de.yu@intel.com>;
> dev@dpdk.org; Zhang, Qi Z <qi.z.zhang@intel.com>
> Subject: [PATCH] net/i40e: remove VF interrupt handler
> 
> For i40evf, internal rx interrupt and adminq interrupt share the same source,
> that cause a lot cpu cycles be wasted on interrupt handler on rx path. This is
> complained by customers which require low latency (when set
> I40E_ITR_INTERVAL to small value), but have to be sufferred by tremendous
> interrupts handling that eat significant CPU resources.
> 
> The patch disable pci interrupt and remove the interrupt handler, replace it
> with a low frequency (50ms) interrupt polling daemon which is implemented
> by registering a alarm callback periodly, this save CPU time significently: On a
> typical x86 server with 2.1GHz CPU, with low latency configure (32us) we saw
> CPU usage from top commmand reduced from 20% to 0% on management
> core in testpmd).
> 
> Also with the new method we can remove compile option:
> I40E_ITR_INTERVAL which is used to balance between low latency and low
> CPU usage previously.
> Now we don't need it since we can reach both at same time.
> 
> Suggested-by: Jingjing Wu <jingjing.wu@intel.com>
> Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
> ---
>  config/common_base                |  2 --
>  drivers/net/i40e/i40e_ethdev.c    |  3 +--
>  drivers/net/i40e/i40e_ethdev.h    | 22 +++++++++++-----------
>  drivers/net/i40e/i40e_ethdev_vf.c | 36 ++++++++++++++----------------------
>  4 files changed, 26 insertions(+), 37 deletions(-)
> 
> diff --git a/config/common_base b/config/common_base index
> 6b0d1cbbb..9e21c6865 100644
> --- a/config/common_base
> +++ b/config/common_base
> @@ -264,8 +264,6 @@ CONFIG_RTE_LIBRTE_I40E_INC_VECTOR=y
>  CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n
>  CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_PF=64
>  CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_VM=4
> -# interval up to 8160 us, aligned to 2 (or default value)
> -CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL=-1

Then description about CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL in documentation should also be removed.

Beilei