Re: [PATCH] igb_uio: use non-threaded ISR
From: Su, David W <hidden>
Date: 2017-01-23 19:20:04
If rte_eth_conf.intr_conf.rxq != 0 and rte_eth_conf.intr_conf.lsc = 0 when rte_eth_dev_configure() is called, rx queue interrupts can be enabled/disabled with rte_eth_dev_rx_intr_{enable|disable} and DPDK applications can wait for rx queue interrupts with rte_epoll_wait(). This is the case for both igb_uio and vfio-pci drivers.
vfio-pci already uses non-threaded ISR, but currently we can only use igb_uio when running DPDK applications in virtual machines.
David
-----Original Message-----
From: Stephen Hemminger [mailto:stephen@networkplumber.org]
Sent: Friday, January 20, 2017 3:51 PM
To: Su, David W <redacted>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] igb_uio: use non-threaded ISR
On Fri, 20 Jan 2017 15:08:19 -0800
David Su [off-list ref] wrote:
quoted hunk ↗ jump to hunk
This eliminates the overhead of a task switch when an interrupt arrives. Signed-off-by: David Su <redacted> --- 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.