netdev - Re: [PATCH net-next 0/2] net: broadcom: Adaptive interrupt coalescing

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Date:   Tue, 27 Mar 2018 00:16:56 +0300
From:   Tal Gilboa <talgi@...lanox.com>
To:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, jaedon.shin@...il.com, pgynther@...gle.com,
        opendmb@...il.com, michal.chan@...adcom.com, gospo@...adcom.com,
        saeedm@...lanox.com
Subject: Re: [PATCH net-next 0/2] net: broadcom: Adaptive interrupt coalescing

On 3/23/2018 4:19 AM, Florian Fainelli wrote:
> Hi all,
> 
> This patch series adds adaptive interrupt coalescing for the Gigabit Ethernet
> drivers SYSTEMPORT and GENET.
> 
> This really helps lower the interrupt count and system load, as measured by
> vmstat for a Gigabit TCP RX session:

I don't see an improvement in system load, the opposite - 42% vs. 100% 
for SYSTEMPORT and 85% vs. 100% for GENET. Both with the same bandwidth. 
Am I missing something? Talking about bandwidth, I would expect 941Mb/s 
(assuming this is TCP over IPv4). Do you know why the reduced interrupt 
rate doesn't improve bandwidth? Also, any effect on the client side (you 
mentioned enabling TX moderation for SYSTEMPORT)?

> 
> SYSTEMPORT:
> 
> without:
> 
>   1  0      0 192188      0  25472    0    0     0     0 122100 38870  1 42 57  0  0
> [ ID] Interval       Transfer     Bandwidth
> [  4]  0.0-10.0 sec  1.03 GBytes   884 Mbits/sec
> 
> with:
> 
>   1  0      0 192288      0  25468    0    0     0     0 58806 44401  0 100  0  0  0
> [  5]  0.0-10.0 sec  1.04 GBytes   888 Mbits/sec
> 
> GENET:
> 
> without:
> 
>   1  0      0 1170404      0  25420    0    0     0     0 130785 63402  2 85 12  0  0
> [ ID] Interval       Transfer     Bandwidth
> [  4]  0.0-10.0 sec  1.04 GBytes   888 Mbits/sec
> 
> with:
> 
>   1  0      0 1170560      0  25420    0    0     0     0 50610 48477  0 100  0  0  0
> [  5]  0.0-10.0 sec  1.05 GBytes   899 Mbits/sec
> 
> Please look at the implementation and let me know if you see any problems, this
> was largely inspired by bnxt_en.
> 
> Thank you!
> 
> Florian Fainelli (2):
>    net: systemport: Implement adaptive interrupt coalescing
>    net: bcmgenet: Add support for adaptive RX coalescing
> 
>   drivers/net/ethernet/broadcom/bcmsysport.c     | 141 ++++++++++++++++++++++---
>   drivers/net/ethernet/broadcom/bcmsysport.h     |  14 +++
>   drivers/net/ethernet/broadcom/genet/bcmgenet.c | 109 +++++++++++++++----
>   drivers/net/ethernet/broadcom/genet/bcmgenet.h |  12 +++
>   4 files changed, 243 insertions(+), 33 deletions(-)
>