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authorJesse Brandeburg <jesse.brandeburg@intel.com>2014-12-19 04:22:06 +0300
committerThomas Gleixner <tglx@linutronix.de>2015-01-23 13:38:25 +0300
commite2e64a932556cdfae455497dbe94a8db151fc9fa (patch)
treed866fe301c51efaeff70822653434363eea4dec2 /kernel/irq/manage.c
parentec6f34e5b552fb0a52e6aae1a5afbbb1605cc6cc (diff)
downloadlinux-e2e64a932556cdfae455497dbe94a8db151fc9fa.tar.xz
genirq: Set initial affinity in irq_set_affinity_hint()
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. Solution: Enable 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 <jesse.brandeburg@intel.com> Cc: netdev@vger.kernel.org Link: http://lkml.kernel.org/r/20141219012206.4220.27491.stgit@jbrandeb-cp2.jf.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/irq/manage.c')
-rw-r--r--kernel/irq/manage.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 80692373abd6..f038e586a4b9 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);