From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752592AbaLSTxJ (ORCPT ); Fri, 19 Dec 2014 14:53:09 -0500 Received: from mail-qc0-f169.google.com ([209.85.216.169]:42082 "EHLO mail-qc0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751165AbaLSTxH (ORCPT ); Fri, 19 Dec 2014 14:53:07 -0500 MIME-Version: 1.0 In-Reply-To: <20141219012206.4220.27491.stgit@jbrandeb-cp2.jf.intel.com> References: <20141219012206.4220.27491.stgit@jbrandeb-cp2.jf.intel.com> Date: Fri, 19 Dec 2014 11:53:06 -0800 Message-ID: Subject: Re: [PATCH] genirq: set initial affinity when hinting From: Jesse Brandeburg To: Jesse Brandeburg Cc: Thomas Gleixner , "linux-kernel@vger.kernel.org" , NetDEV list Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +netdev, as network driver developers might be interested in this functionality. On Thu, Dec 18, 2014 at 5:22 PM, Jesse Brandeburg wrote: > Problem: > The default behavior of the kernel is somewhat undesirable as all > requested interrupts end up on CPU0 after registration. A user can > run irqbalance daemon, or can manually configure smp_affinity via the > proc filesystem, but the default affinity of the interrupts for all > devices is always CPU zero, this can cause performance problems or > very heavy cpu use of only one core if not noticed and fixed by the > user. > > Patch: > This patch enables the setting of the initial affinity directly > when the driver sets a hint. > > This enabling means that kernel drivers can include an initial > affinity setting for the interrupt, instead of all interrupts starting > out life on CPU0. Of course if irqbalance is still running then the > interrupts will get moved as before. > > This function is currently called by drivers in block, crypto, > infiniband, ethernet and scsi trees, but only a handful, so these will > be the devices affected by this change. > > Tested on i40e, and default interrupts were spread across the CPUs > according to the hint. > > drivers/block/mtip32xx/mtip32xx.c:3 > drivers/block/nvme-core.c:2 > drivers/crypto/qat/qat_dh895xcc/adf_isr.c:3 > drivers/infiniband/hw/qib/qib_iba7322.c:2 > drivers/net/ethernet/intel/i40e/i40e_main.c:3 > drivers/net/ethernet/intel/i40evf/i40evf_main.c:3 > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c:3 > drivers/net/ethernet/mellanox/mlx4/en_cq.c:2 > drivers/scsi/hpsa.c:3 > drivers/scsi/lpfc/lpfc_init.c:3 > drivers/scsi/megaraid/megaraid_sas_base.c:8 > drivers/soc/ti/knav_qmss_acc.c:1 > drivers/soc/ti/knav_qmss_queue.c:2 > drivers/virtio/virtio_pci_common.c:2 > > Signed-off-by: Jesse Brandeburg > CC: Thomas Gleixner > --- > kernel/irq/manage.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > index 8069237..f038e58 100644 > --- a/kernel/irq/manage.c > +++ b/kernel/irq/manage.c > @@ -243,6 +243,8 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) > return -EINVAL; > desc->affinity_hint = m; > irq_put_desc_unlock(desc, flags); > + /* set the initial affinity to prevent every interrupt being on CPU0 */ > + __irq_set_affinity(irq, m, false); > return 0; > } > EXPORT_SYMBOL_GPL(irq_set_affinity_hint); >