Re: [dpdk-dev] [PATCH v2 2/3] net/af_xdp: support pinning of IRQs

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 10/14/2019 3:43 PM, Bruce Richardson wrote:
> On Thu, Oct 03, 2019 at 02:23:07PM +0100, Loftus, Ciara wrote:
>>
>>
>>> -----Original Message----- From: Stephen Hemminger
>>> <stephen@networkplumber.org> Sent: Monday 30 September 2019 18:12 To:
>>> Loftus, Ciara <ciara.loftus@intel.com> Cc: dev@dpdk.org; Ye, Xiaolong
>>> <xiaolong.ye@intel.com>; Laatz, Kevin <kevin.laatz@intel.com>;
>>> Richardson, Bruce <bruce.richardson@intel.com> Subject: Re: [dpdk-dev]
>>> [PATCH v2 2/3] net/af_xdp: support pinning of IRQs
>>>
>>> On Mon, 30 Sep 2019 16:42:04 +0000 Ciara Loftus
>>> <ciara.loftus@intel.com> wrote:
>>>
>>>> +/* drivers supported for the queue_irq option */ +enum
>>>> supported_drivers { +	I40E_DRIVER, +	IXGBE_DRIVER, +
>>>> MLX5_DRIVER, +	NUM_DRIVERS +};
>>>
>>> Anything device specific like this raises a red flag to me.
>>>
>>> This regex etc, seems like a huge hack. Is there a better way  using
>>> irqbalance and smp_affinity in kernel drivers?
>>>
>>> NACK
>>
>> Hi Stephen,
>>  
>> Thanks for looking at the patch. I understand your concern however
>> unfortunately I haven't been able to identify a way to achieve the
>> desired outcome by using your suggestions of irqbalance and smp_affinity.
>> Did you have something specific in mind or are aware of any generic way
>> of retrieving interrupt numbers for NICs regardless of vendor or range?
>>  
>> I think this feature is really important for the usability of this PMD.
>> Without it, to configure the IRQs the user has to open up
>> /proc/interrupts, trawl through it and identify the correct IRQ number
>> for their given NIC and qid (the format for which is unlikely to be known
>> off-hand), and manually pin them by writing the appropriate values in the
>> appropriate format to the appropriate file - prone to error if not
>> automated IMO.  If the user fails to set the affinity it's probably fine
>> for a single pmd, however with multiple pmds all irqs will by default
>> land on core 0 and lead to terrible performance.
>>
>> It should be possible to rework the code to remove the regexes and use a
>> direct string compare. Would that make the solution more palatable?
>>  
> 
> Hi Ciara, Stephen,
> 
> is there any way forward on this patch?
> 
> From my experience with using AF_XDP the pinning of interrupts is both
> necessary for performance and sadly rather awkward to implement in
> practice. If we can't find a better way to do this, I think merging this
> patch is the best thing to do. It may be a bit messy, but the overall user
> experience should be far improved over not having it.
> 

Can we have this external to the PMD, like a helper script that run after you
start the DPDK app?