linux-kernel - Re: [PATCH net-next v4 2/5] page_frag: unify gfp bits for order 3 page allocation

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Date: Fri, 2 Feb 2024 20:26:19 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Paolo Abeni <pabeni@...hat.com>, <davem@...emloft.net>, <kuba@...nel.org>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Alexander Duyck
	<alexanderduyck@...com>, Alexander Duyck <alexander.duyck@...il.com>,
	"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, Eric Dumazet
	<edumazet@...gle.com>, <kvm@...r.kernel.org>,
	<virtualization@...ts.linux.dev>, <linux-mm@...ck.org>
Subject: Re: [PATCH net-next v4 2/5] page_frag: unify gfp bits for order 3
 page allocation

On 2024/2/2 16:36, Paolo Abeni wrote:
> On Fri, 2024-02-02 at 10:10 +0800, Yunsheng Lin wrote:
>> On 2024/2/1 21:16, Paolo Abeni wrote:
>>
>>> from the __page_frag_cache_refill() allocator - which never accesses
>>> the memory reserves.
>>
>> I am not really sure I understand the above commemt.
>> The semantic is the same as skb_page_frag_refill() as explained above
>> as my understanding. Note that __page_frag_cache_refill() use 'gfp_mask'
>> for allocating order 3 pages and use the original 'gfp' for allocating
>> order 0 pages.
> 
> You are right! I got fooled misreading 'gfp' as 'gfp_mask' in there.
> 
>>> I'm unsure we want to propagate the __page_frag_cache_refill behavior
>>> here, the current behavior could be required by some systems.
>>>
>>> It looks like this series still leave the skb_page_frag_refill()
>>> allocator alone, what about dropping this chunk, too? 
>>
>> As explained above, I would prefer to keep it as it is as it seems
>> to be quite obvious that we can avoid possible pressure for mm by
>> not using memory reserve for order 3 pages as we have the fallback
>> for order 0 pages.
>>
>> Please let me know if there is anything obvious I missed.
>>
> 
> I still think/fear that behaviours changes here could have
> subtle/negative side effects - even if I agree the change looks safe.
> 
> I think the series without this patch would still achieve its goals and
> would be much more uncontroversial. What about move this patch as a
> standalone follow-up?

Fair enough, will remove that for now.

> 
> Thanks!
> 
> Paolo
> 
> .
>