From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751750AbaLSBWX (ORCPT ); Thu, 18 Dec 2014 20:22:23 -0500 Received: from mga03.intel.com ([134.134.136.65]:39999 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751649AbaLSBWW (ORCPT ); Thu, 18 Dec 2014 20:22:22 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,604,1413270000"; d="scan'208";a="626317801" Subject: [PATCH] genirq: set initial affinity when hinting To: tglx@linutronix.de From: Jesse Brandeburg Cc: linux-kernel@vger.kernel.org Date: Thu, 18 Dec 2014 17:22:06 -0800 Message-ID: <20141219012206.4220.27491.stgit@jbrandeb-cp2.jf.intel.com> User-Agent: StGit/0.16-44-gd947d-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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);