linux-kernel - Re: [PATCH 09/22] [SCSI] mpt2sas, mpt3sas: Added a support to set cpu affinity for each MSIX vector enabled by the HBA

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Message-ID: <CAK=zhgq12Go0YXY+msuoeXeUoRJZQ=hKqChuoesaAzu-T=FjpA@mail.gmail.com>
Date:	Thu, 11 Dec 2014 17:21:33 +0530
From:	Sreekanth Reddy <sreekanth.reddy@...gotech.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	jejb@...nel.org, Christoph Hellwig <hch@...radead.org>,
	linux-scsi@...r.kernel.org,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	Sathya Prakash <Sathya.Prakash@...gotech.com>,
	Nagalakshmi Nandigama <Nagalakshmi.Nandigama@...gotech.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/22] [SCSI] mpt2sas, mpt3sas: Added a support to set cpu
 affinity for each MSIX vector enabled by the HBA

> @@ -1373,20 +1380,30 @@ _base_assign_reply_queues(struct MPT2SAS_ADAPTER *ioc)
>
>         cpu = cpumask_first(cpu_online_mask);
>
> -       do {
> +       list_for_each_entry(reply_q, &ioc->reply_queue_list, list) {
> +
>
> Why are you reverting to iterating over the queues? A while back I fixed
> this up so it wouldn't fail when nr_cpus > the number of reply queues.
>

I have kept yours CPUs affinity with reply queues logic as it is. This
patch doesn't break any of it's original CPUs affinity with reply
queues calculation  even when nr_cpus > the number of reply queues.
since below loop will help us to calculate CPU groups which needs to
affinity to particular reply queue when nr_cpus > the number of reply
queues

               for (i = 0 ; i < group ; i++) {
                        ioc->cpu_msix_table[cpu] = index;
+                       cpumask_or(reply_q->affinity_hint,
+                                  reply_q->affinity_hint, get_cpu_mask(cpu));
                        cpu = cpumask_next(cpu, cpu_online_mask);
                }

I am iterating over the queues to get the MSIX vector number easily,
while calling irq_set_affinity_hint() API for setting CPUs affinity
hint for that MSIX vector.

Regards,
Sreekanth
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