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Subject: Re: [Patch v1] i40e: limit the msix vectors based on housekeeping
 CPUs
To:     Christoph Hellwig <hch@infradead.org>
Cc:     linux-kernel@vger.kernel.org, frederic@kernel.org,
        mtosatti@redhat.com, sassmann@redhat.com,
        jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com,
        jlelli@redhat.com
References: <20200615202125.27831-1-nitesh@redhat.com>
 <20200615202125.27831-2-nitesh@redhat.com>
 <20200616080309.GA21210@infradead.org>
From:   Nitesh Narayan Lal <nitesh@redhat.com>
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Date:   Fri, 26 Jun 2020 16:11:24 -0400
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On 6/16/20 4:03 AM, Christoph Hellwig wrote:
> On Mon, Jun 15, 2020 at 04:21:25PM -0400, Nitesh Narayan Lal wrote:
>> +=09hk_flags =3D HK_FLAG_DOMAIN | HK_FLAG_WQ;
>> +=09mask =3D housekeeping_cpumask(hk_flags);
>> +=09cpus =3D cpumask_weight(mask);
> Code like this has no business inside a driver.  Please provide a
> proper core API for it instead.  Also please wire up
> pci_alloc_irq_vectors* to use this API as well.
>

Hi Christoph,

I have been looking into using nr_houskeeping_* API that I will be defining
within pci_alloc_irq_vectors* to limit the nr of vectors.
However, I am wondering about a few things:

- Some of the drivers such as i40e until now, use the num_online CPUs to
=C2=A0 restrict the number of vectors that they should create. Will it make=
 sense if
=C2=A0 I restrict the maximum vectors requested based on
=C2=A0 nr_online/housekeeping_cpus (Though I will have to make sure that th=
e
=C2=A0 min_vecs is always satisfied)?

=C2=A0 The other option would be to check for the total available vectors i=
n all
=C2=A0 online/housekeeping CPUs for limiting the maxvecs, this way will pro=
bably be
=C2=A0 more accurate?

- Another thing that I am wondering about is the right way to test this cha=
nge.

Please let me know if you have any suggestions?

--=20
Nitesh


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