netdev - Re: [PATCH net-next 0/4] eth: mlx4: use the page pool for Rx buffers

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Message-ID: <1c187a13-977d-4dae-a9eb-18ef602f5682@gmail.com>
Date: Tue, 11 Feb 2025 20:05:01 +0200
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
 tariqt@...dia.com, hawk@...nel.org
Subject: Re: [PATCH net-next 0/4] eth: mlx4: use the page pool for Rx buffers



On 06/02/2025 17:58, Jakub Kicinski wrote:
> On Thu, 6 Feb 2025 14:57:59 +0200 Tariq Toukan wrote:
>> On 05/02/2025 5:12, Jakub Kicinski wrote:
>>> Convert mlx4 to page pool. I've been sitting on these patches for
>>> over a year, and Jonathan Lemon had a similar series years before.
>>> We never deployed it or sent upstream because it didn't really show
>>> much perf win under normal load (admittedly I think the real testing
>>> was done before Ilias's work on recycling).
>>>
>>> During the v6.9 kernel rollout Meta's CDN team noticed that machines
>>> with CX3 Pro (mlx4) are prone to overloads (double digit % of CPU time
>>> spent mapping buffers in the IOMMU). The problem does not occur with
>>> modern NICs, so I dusted off this series and reportedly it still works.
>>> And it makes the problem go away, no overloads, perf back in line with
>>> older kernels. Something must have changed in IOMMU code, I guess.
>>>
>>> This series is very simple, and can very likely be optimized further.
>>> Thing is, I don't have access to any CX3 Pro NICs. They only exist
>>> in CDN locations which haven't had a HW refresh for a while. So I can
>>> say this series survives a week under traffic w/ XDP enabled, but
>>> my ability to iterate and improve is a bit limited.
>>
>> Hi Jakub,
>>
>> Thanks for your patches.
>>
>> As this series touches critical data-path area, and you had no real
>> option of testing it, we are taking it through a regression cycle, in
>> parallel to the code review.
>>
>> We should have results early next week. We'll update.
> 
> Sounds good, could you repost once ready?
> I'll mark it as awaiting upstream in patchwork for now.
> And feel free to drop the line pointed out by Ido, no real
> preference either way there.

Hi,

Patches passed functional tests.

Overall, the patches look good.

Only a few comments:
1. Nit by Ido.
2. pool size.
3. xdp xmit support description.

How do you want to proceed?
Do you want to fix and re-spin?