| From ca8c7c0106d07af6d1070645c5127c30e317196f Mon Sep 17 00:00:00 2001 |
| From: Long Li <longli@microsoft.com> |
| Date: Fri, 2 Nov 2018 18:02:48 +0000 |
| Subject: genirq/affinity: Spread IRQs to all available NUMA nodes |
| |
| [ Upstream commit b82592199032bf7c778f861b936287e37ebc9f62 ] |
| |
| If the number of NUMA nodes exceeds the number of MSI/MSI-X interrupts |
| which are allocated for a device, the interrupt affinity spreading code |
| fails to spread them across all nodes. |
| |
| The reason is, that the spreading code starts from node 0 and continues up |
| to the number of interrupts requested for allocation. This leaves the nodes |
| past the last interrupt unused. |
| |
| This results in interrupt concentration on the first nodes which violates |
| the assumption of the block layer that all nodes are covered evenly. As a |
| consequence the NUMA nodes above the number of interrupts are all assigned |
| to hardware queue 0 and therefore NUMA node 0, which results in bad |
| performance and has CPU hotplug implications, because queue 0 gets shut |
| down when the last CPU of node 0 is offlined. |
| |
| Go over all NUMA nodes and assign them round-robin to all requested |
| interrupts to solve this. |
| |
| [ tglx: Massaged changelog ] |
| |
| Signed-off-by: Long Li <longli@microsoft.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Reviewed-by: Ming Lei <ming.lei@redhat.com> |
| Cc: Michael Kelley <mikelley@microsoft.com> |
| Link: https://lkml.kernel.org/r/20181102180248.13583-1-longli@linuxonhyperv.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| kernel/irq/affinity.c | 5 ++--- |
| 1 file changed, 2 insertions(+), 3 deletions(-) |
| |
| diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c |
| index f4f29b9d90ee..e12cdf637c71 100644 |
| --- a/kernel/irq/affinity.c |
| +++ b/kernel/irq/affinity.c |
| @@ -117,12 +117,11 @@ static int irq_build_affinity_masks(const struct irq_affinity *affd, |
| */ |
| if (numvecs <= nodes) { |
| for_each_node_mask(n, nodemsk) { |
| - cpumask_copy(masks + curvec, node_to_cpumask[n]); |
| - if (++done == numvecs) |
| - break; |
| + cpumask_or(masks + curvec, masks + curvec, node_to_cpumask[n]); |
| if (++curvec == last_affv) |
| curvec = affd->pre_vectors; |
| } |
| + done = numvecs; |
| goto out; |
| } |
| |
| -- |
| 2.19.1 |
| |
