Re: [Intel-wired-lan] [PATCH net-next v5 03/14] page_pool: avoid calling no-op externals when possible

[Alexander Lobakin]

From: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
Date: Thu, 30 Nov 2023 16:46:11 +0800

> On 2023/11/29 21:17, Alexander Lobakin wrote:
>> From: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
>> Date: Wed, 29 Nov 2023 11:17:50 +0800
>>
>>> On 2023/11/27 22:32, Alexander Lobakin wrote:
>>>>
>>>> Chris, any thoughts on a global flag for skipping DMA syncs ladder?
>>>
>>> It seems there was one already in the past:
>>>
>>> https://lore.kernel.org/netdev/7c55a4d7-b4aa-25d4-1917-f6f355bd722e@xxxxxxx/T/
>>
>> It addresses a different problem, meaningless indirect calls, while this
>> one addresses meaningless direct calls :>
>> When the above gets merged, we could combine these two into one global,
>> but Eric wasn't active with his patch and I remember there were some
>> problems, so I wouldn't count on that it will arrive soon.
> 
> I went through the above patch, It seems to me that there was no
> fundamental problem that stopping us from implementing it in the dma
> layer basing on Eric' patch if Eric is no longer interested in working
> on a newer version?

I'm somewhat interested in continuing working on Eric's patch, but not
now. Have some urgent projects to work on, I could take this in January
I guess...
This PP-specific shortcut was done earlier and gives good boosts. It
would be trivial to remove it together with the XSk shortcut once a
generic both indirect and direct call DMA shortcut lands.
Does this sounds good / justified enough? Or you and other
reviewers/maintainers would prefer to wait for the generic one without
taking this patch?

> 
> It is just that if we allow every subsystem and driver using dma API
> doing their own trick of skipping dma sync, then there is less willing
> to implement it in the dma layer.

Thanks,
Olek