Date: Mon, 12 Feb 2024 23:53:03 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Paul Barker <paul.barker.ct@...renesas.com>, "David S . Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, Wolfram Sang
	<wsa+renesas@...g-engineering.com>, <netdev@...r.kernel.org>,
	<linux-renesas-soc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH net-next v2 0/7] Improve GbEth performance on Renesas
 RZ/G2L and related SoCs

On 2/12/24 2:52 PM, Paul Barker wrote:
[...]

>>> This series aims to improve peformance of the GbEth IP in the Renesas
>>
>>    You didn't fix the typo in "peformance"... :-/
>>
>>> RZ/G2L SoC family and the RZ/G3S SoC, which use the ravb driver. Along
>>> the way, we do some refactoring and ensure that napi_complete_done() is
>>> used in accordance with the NAPI documentation for both GbEth and R-Car
>>> code paths.
>>>
>>> Performance improvment mainly comes from enabling SW IRQ Coalescing for
>>
>>    And in "improvment" too... :-/
> 
> I'll fix this and the above type in v3.

   TIA! Chances are this will end up in the merge commit...

>>> all SoCs using the GbEth IP, and NAPI Threaded mode for single core SoCs
>>> using the GbEth IP. These can be enabled/disabled at runtime via sysfs,
>>> but our goal is to set sensible defaults which get good performance on
>>> the affected SoCs.
>>>
>>> The performance impact of this series on iperf3 testing is as follows:
>>>   * RZ/G2L Ethernet throughput is unchanged, but CPU usage drops:
>>>       * Bidirectional and TCP RX: 6.5% less CPU usage
>>>       * UDP RX: 10% less CPU usage
>>>
>>>   * RZ/G2UL and RZ/G3S Ethernet throughput is increased for all test
>>>     cases except UDP TX, which suffers a slight loss:
>>>       * TCP TX: 32% more throughput
>>>       * TCP RX: 11% more throughput
>>>       * UDP TX: 10% less throughput
>>>       * UDP RX: 10183% more throughput - the previous throughput of
>>
>>    So this is a real figure? I thought you forgot to erase 10... :-)
> 
> Yes, throughput went from 1.06Mbps to 109Mbps for the RZ/G2UL with these
> changes.

   Hm, that gives me even 10283%! :-)

> Initial testing shows that goes up again to 485Mbps with the next patch
> series I'm working on to reduce RX buffer sizes.

   Oh, wow! :-)

> Biju's work on checksum offload also helps a lot with these numbers, I
> can't take all the credit.

   Took 5 versions to merge, unfortunately... :-/

[...]

>>> Work in this area will continue, in particular we expect to improve
>>> TCP/UDP RX performance further with future changes to RX buffer
>>> handling.
>>>
>>> Changes v1->v2:
>>>   * Marked as RFC as the series depends on unmerged patches.
>>>   * Refactored R-Car code paths as well as GbEth code paths.
>>>   * Updated references to the patches this series depends on.
>>>
>>> Paul Barker (7):
>>>   net: ravb: Simplify poll & receive functions
>>
>>    The below 3 commits fix issues in the GbEth code, so should
>> be redone against net.git and posted separately from this series...
>>
>>>   net: ravb: Count packets instead of descriptors in RX path
>>>   net: ravb: Always process TX descriptor ring
>>>   net: ravb: Always update error counters
> 
> I'll split out and re-submit these as bug fixes. "net: ravb: Count
> packets instead of descriptors in RX path" will require a bit of rework
> so it doesn't depend on the first patch of the series ("net: ravb:
> Simplify poll & receive functions") so you'll probably want to re-review
> when I send it.

   Yes, I figured that at least the 1st patch would need to be reworked...

> Then I'll re-send the rest as a non-RFC series.

   Won't they need to be rebased against 3 fixes?

[...]

> Thanks for the review!
> Paul

MBR, Sergey

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