netdev - Re: [net-next 04/17] drivers/net/intel: use napi_complete

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Date:	Thu, 12 Nov 2015 21:18:16 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:	davem@...emloft.net, Jesse Brandeburg <jesse.brandeburg@...el.com>,
	netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
	jogreene@...hat.com
Subject: Re: [net-next 04/17] drivers/net/intel: use napi_complete_done()

On Thu, 2015-10-15 at 14:43 -0700, Jeff Kirsher wrote:
> From: Jesse Brandeburg <jesse.brandeburg@...el.com>
> 
> As per Eric Dumazet's previous patches:
> (see commit (24d2e4a50737) - tg3: use napi_complete_done())
> 
> Quoting verbatim:
> Using napi_complete_done() instead of napi_complete() allows
> us to use /sys/class/net/ethX/gro_flush_timeout
> 
> GRO layer can aggregate more packets if the flush is delayed a bit,
> without having to set too big coalescing parameters that impact
> latencies.
> </end quote>
> 
> Tested
> configuration: low latency via ethtool -C ethx adaptive-rx off
> 				rx-usecs 10 adaptive-tx off tx-usecs 15
> workload: streaming rx using netperf TCP_MAERTS
> 
> igb:
> MIGRATED TCP MAERTS TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.0.1 () port 0 AF_INET : demo
> ...
> Interim result:  941.48 10^6bits/s over 1.000 seconds ending at 1440193171.589
> 
> Alignment      Offset         Bytes    Bytes       Recvs   Bytes    Sends
> Local  Remote  Local  Remote  Xfered   Per                 Per
> Recv   Send    Recv   Send             Recv (avg)          Send (avg)
>     8       8      0       0 1176930056  1475.36    797726   16384.00  71905
> 
> MIGRATED TCP MAERTS TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.0.1 () port 0 AF_INET : demo
> ...
> Interim result:  941.49 10^6bits/s over 0.997 seconds ending at 1440193142.763
> 
> Alignment      Offset         Bytes    Bytes       Recvs   Bytes    Sends
> Local  Remote  Local  Remote  Xfered   Per                 Per
> Recv   Send    Recv   Send             Recv (avg)          Send (avg)
>     8       8      0       0 1175182320  50476.00     23282   16384.00  71816
> 
> i40e:
> Hard to test because the traffic is incoming so fast (24Gb/s) that GRO
> always receives 87kB, even at the highest interrupt rate.
> 
> Other drivers were only compile tested.
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>


Hi guys

I am not sure the ixgbe part is working :

ixgbe_qv_unlock_napi() does :

/* flush any outstanding Rx frames */
if (q_vector->napi.gro_list)
        napi_gro_flush(&q_vector->napi, false);

And it is called before napi_complete_done(napi, work_done);



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