netdev - Re: [PATCH iwl-next] idpf: preserve coalescing settings across resets

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Message-ID: <4adc2963-a5f2-459c-9535-301e207f8cb2@intel.com>
Date: Tue, 24 Jun 2025 10:13:38 -0600
From: Ahmed Zaki <ahmed.zaki@...el.com>
To: Simon Horman <horms@...nel.org>
CC: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>, "Madhu
 Chittim" <madhu.chittim@...el.com>
Subject: Re: [PATCH iwl-next] idpf: preserve coalescing settings across resets



On 2025-06-24 3:40 a.m., Simon Horman wrote:
> On Mon, Jun 23, 2025 at 09:48:02AM -0600, Ahmed Zaki wrote:
>>
>>
>> On 2025-06-21 6:13 a.m., Simon Horman wrote:
>>> On Fri, Jun 20, 2025 at 11:15:48AM -0600, Ahmed Zaki wrote:
>>>> The IRQ coalescing config currently reside only inside struct
>>>> idpf_q_vector. However, all idpf_q_vector structs are de-allocated and
>>>> re-allocated during resets. This leads to user-set coalesce configuration
>>>> to be lost.
>>>>
>>>> Add new fields to struct idpf_vport_user_config_data to save the user
>>>> settings and re-apply them after reset.
>>>>
>>>> Reviewed-by: Madhu Chittim <madhu.chittim@...el.com>
>>>> Signed-off-by: Ahmed Zaki <ahmed.zaki@...el.com>
>>>
>>> Hi Ahmed,
>>>
>>> I am wondering if this patch also preserves coalescing settings in the case
>>> where.
>>>
>>> 1. User sets coalescence for n queues
>>> 2. The number of queues is reduced, say to m (where m < n)
>>> 3. The user then increases the number of queues, say back to n
>>>
>>> It seems to me that in this scenario it's reasonable to preserve
>>> the settings for queues 0 to m, bit not queues m + 1 to n.
>>
>> Hi Simon,
>>
>> I just did a quick test and it seems new settings are preserved in the above
>> scenario: all n queues have the new coalescing settings.
> 
> Hi Ahmed,
> 
> Thanks for looking into this.
> 
>>> But perhaps this point is orthogonal to this change.
>>> I am unsure.
>>>
>>
>> Agreed, but let me know if it is a showstopper.
> 
> If preserving the status of all n queues, rather than just the first m
> queues, in the scenario described above is new behaviour added by this
> patch then I would lean towards yes. Else no.
> 
>

I don't believe we can call this new behavior. Actually, the napi IRQ 
affinity pushed to CORE few weeks ago behaves in the same manner; 
deleting queues and re-adding them restores the user-set IRQ affinity.