linux-kernel - Re: [RFC PATCH net-next v2 0/7] Improve GbEth performance on Renesas RZ/G2L and related SoCs

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Date: Wed, 14 Feb 2024 09:17:15 +0000
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Sergey Shtylyov <s.shtylyov@....ru>,
 "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 12/02/2024 20:53, Sergey Shtylyov wrote:
> 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?

Yes, the rest will need rebasing.

We need to test gPTP on an RZ/G2N board with these changes first. We're
working on it and I'll let you know the status soon. I should be able to
send at least one bugfix in a way that doesn't affect RZ/G2N & R-Car
boards though...

Thanks,

-- 
Paul Barker
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