Re: [patch net-next v7 0/3] return offloaded stats as default and expose original sw stats

[Roopa Prabhu]

On 9/5/16, 10:18 AM, Jiri Pirko wrote:
> From: Jiri Pirko 
>
> The problem we try to handle is about offloaded forwarded packets
> which are not seen by kernel. Let me try to draw it:
>
> port1   port2 (HW stats are counted here)
>   \  /
>\/
> \  /
>  --(A) ASIC --(B)--
> |
>(C)
> |
>CPU (SW stats are counted here)
>
>
> Now we have couple of flows for TX and RX (direction does not matter here):
>
> 1) port1->A->ASIC->C->CPU
>
>For this flow, HW and SW stats are equal.
>
> 2) port1->A->ASIC->C->CPU->C->ASIC->B->port2
>
>For this flow, HW and SW stats are equal.
>
> 3) port1->A->ASIC->B->port2
>
>For this flow, SW stats are 0.
>
> The purpose of this patchset is to provide facility for user to
> find out the difference between flows 1+2 and 3. In other words, user
> will be able to see the statistics for the slow-path (through kernel).
>
> Also note that HW stats are what someone calls "accumulated" stats.
> Every packet counted by SW is also counted by HW. Not the other way around.
>
> As a default the accumulated stats (HW) will be exposed to user
> so the userspace apps can react properly.
>
> This patchset add the SW stats (flows 1+2) under offload related stats, so
> in the future we can expose other offload related stat in a similar way.
>
> ---
>
Acked-by: Roopa Prabhu 
few questions on the two ndo's on specific patches, but, the user api LGTM.

thanks jiri and nogah.

[patch net-next v7 0/3] return offloaded stats as default and expose original sw stats

[Jiri Pirko]

From: Jiri Pirko 

The problem we try to handle is about offloaded forwarded packets
which are not seen by kernel. Let me try to draw it:

port1   port2 (HW stats are counted here)
  \  /
   \/
\  /
 --(A) ASIC --(B)--
|
   (C)
|
   CPU (SW stats are counted here)


Now we have couple of flows for TX and RX (direction does not matter here):

1) port1->A->ASIC->C->CPU

   For this flow, HW and SW stats are equal.

2) port1->A->ASIC->C->CPU->C->ASIC->B->port2

   For this flow, HW and SW stats are equal.

3) port1->A->ASIC->B->port2

   For this flow, SW stats are 0.

The purpose of this patchset is to provide facility for user to
find out the difference between flows 1+2 and 3. In other words, user
will be able to see the statistics for the slow-path (through kernel).

Also note that HW stats are what someone calls "accumulated" stats.
Every packet counted by SW is also counted by HW. Not the other way around.

As a default the accumulated stats (HW) will be exposed to user
so the userspace apps can react properly.

This patchset add the SW stats (flows 1+2) under offload related stats, so
in the future we can expose other offload related stat in a similar way.

---
v6->v7:
- patch 1/3:
 - ndo interface changed to get the wanted stats type as an input.
 - change commit message.
- patch 2/3:
 - create a nesting for offloaded stat and put SW stats under it.
 - change the ndo call to indicate which offload stats we wants.
 - change commit message.
- patch 3/3:
 - change ndo implementation to match the changes in the previous patches.
 - change commit message.
v5->v6:
- patch 2/4 was dropped as requested by Roopa
- patch 1/3:
 - comment changed to indicate that default stats are combined stats
 - commit massage changed
- patch 2/3: (previously 3/4)
 - SW stats return nothing if there is no SW stats ndo
v4->v5:
- updated cover letter
- patch3/4:
  - using memcpy directly to copy stats as requested by DaveM
v3->v4:
- patch1/4:
  - fixed "return ()" pointed out by EricD
- patch2/4:
  - fixed if_nlmsg_size as pointed out by EricD
v2->v3:
- patch1/4:
  - added dev_have_sw_stats helper
- patch2/4:
  - avoided memcpy as requested by DaveM
- patch3/4:
  - use new dev_have_sw_stats helper
v1->v2:
- patch3/4:
  - fixed NULL initialization

Nogah Frankel (3):
  netdevice: Add offload statistics ndo
  net: core: Add offload stats to if_stats_msg
  mlxsw: spectrum: Implement offload stats ndo and expose HW stats by
default

 drivers/net/ethernet/mellanox/mlxsw/spectrum.c | 129 +++--
 drivers/net/ethernet/mellanox/mlxsw/spectrum.h |   5 +
 include/linux/netdevice.h  |  12 +++
 include/uapi/linux/if_link.h   |  10 ++
 net/core/rtnetlink.c   |  88 -
 5 files changed, 233 insertions(+), 11 deletions(-)

-- 
2.5.5