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Date: Fri, 20 Jan 2017 15:50:58 -0800
From: Stephen Hemminger <stephen@networkplumber.org>
To: David Su <david.w.su@intel.com>
Cc: dev@dpdk.org
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Subject: Re: [dpdk-dev] [PATCH] igb_uio: use non-threaded ISR
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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.