From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH] igb_uio: use non-threaded ISR
Date: Fri, 20 Jan 2017 15:50:58 -0800
Message-ID: <20170120155058.5177efc4@xeon-e3>
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To: David Su <david.w.su@intel.com>
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On Fri, 20 Jan 2017 15:08:19 -0800
David Su <david.w.su@intel.com> wrote:

> This eliminates the overhead of a task switch when an interrupt arrives.
> 
> Signed-off-by: David Su <david.w.su@intel.com>
> ---
>  lib/librte_eal/linuxapp/igb_uio/igb_uio.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
> index df41e45..9338e14 100644
> --- a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
> +++ b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
> @@ -382,6 +382,7 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  		msix_entry.entry = 0;
>  		if (pci_enable_msix(dev, &msix_entry, 1) == 0) {
>  			dev_dbg(&dev->dev, "using MSI-X");
> +			udev->info.irq_flags = IRQF_NO_THREAD;
>  			udev->info.irq = msix_entry.vector;
>  			udev->mode = RTE_INTR_MODE_MSIX;
>  			break;
> @@ -390,7 +391,7 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  	case RTE_INTR_MODE_LEGACY:
>  		if (pci_intx_mask_supported(dev)) {
>  			dev_dbg(&dev->dev, "using INTX");
> -			udev->info.irq_flags = IRQF_SHARED;
> +			udev->info.irq_flags = IRQF_SHARED | IRQF_NO_THREAD;
>  			udev->info.irq = dev->irq;
>  			udev->mode = RTE_INTR_MODE_LEGACY;
>  			break;

Since interrupts are only used for link state transistions with igb_uio,
I can't see how the overhead of task switch would matter.