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

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Message-ID: <4814a337-454b-d476-dabe-5035dd6dc51f@huawei.com>
Date:   Thu, 30 Nov 2023 16:46:11 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.com>,
        Christoph Hellwig <hch@....de>
CC:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        <netdev@...r.kernel.org>, Alexander Duyck <alexanderduyck@...com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        <linux-kernel@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>,
        Michal Kubiak <michal.kubiak@...el.com>,
        <intel-wired-lan@...ts.osuosl.org>,
        David Christensen <drc@...ux.vnet.ibm.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH net-next v5 03/14] page_pool: avoid
 calling no-op externals when possible

On 2023/11/29 21:17, Alexander Lobakin wrote:
> From: Yunsheng Lin <linyunsheng@...wei.com>
> 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@arm.com/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?

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.