Messages in this thread | | | Date | Thu, 15 Dec 2016 10:24:25 +1100 | From | Gavin Shan <> | Subject | Re: [PATCH] genirq/affinity: fix node generation from cpumask |
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On Wed, Dec 14, 2016 at 04:01:12PM -0200, Guilherme G. Piccoli wrote: >Commit 34c3d9819fda ("genirq/affinity: Provide smarter irq spreading >infrastructure") introduced a better IRQ spreading mechanism, taking >account of the available NUMA nodes in the machine. > >Problem is that the algorithm of retrieving the nodemask iterates >"linearly" based on the number of online nodes - some architectures >present non-linear node distribution among the nodemask, like PowerPC. >If this is the case, the algorithm lead to a wrong node count number >and therefore to a bad/incomplete IRQ affinity distribution. > >For example, this problem were found in a machine with 128 CPUs and two >nodes, namely nodes 0 and 8 (instead of 0 and 1, if it was linearly >distributed). This led to a wrong affinity distribution which then led to >a bad mq allocation for nvme driver. > >Finally, we take the opportunity to fix a comment regarding the affinity >distribution when we have _more_ nodes than vectors. > >Fixes: 34c3d9819fda ("genirq/affinity: Provide smarter irq spreading infrastructure") >Reported-by: Gabriel Krisman Bertazi <gabriel@krisman.be> >Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com> >Cc: stable@vger.kernel.org # v4.9+ >Cc: Christoph Hellwig <hch@lst.de> >Cc: linuxppc-dev@lists.ozlabs.org >Cc: linux-pci@vger.kernel.org >---
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
There is one picky comment as below, but you don't have to fix it :)
> kernel/irq/affinity.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > >diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c >index 9be9bda..464eaf0 100644 >--- a/kernel/irq/affinity.c >+++ b/kernel/irq/affinity.c >@@ -37,15 +37,15 @@ static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk, > > static int get_nodes_in_cpumask(const struct cpumask *mask, nodemask_t *nodemsk) > { >- int n, nodes; >+ int n, nodes = 0; > > /* Calculate the number of nodes in the supplied affinity mask */ >- for (n = 0, nodes = 0; n < num_online_nodes(); n++) { >+ for_each_online_node(n) > if (cpumask_intersects(mask, cpumask_of_node(n))) { > node_set(n, *nodemsk); > nodes++; > } >- } >+
It'd better to keep the brackets so that we needn't add them when adding more code into the block next time.
> return nodes; > } > >@@ -82,7 +82,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd) > nodes = get_nodes_in_cpumask(cpu_online_mask, &nodemsk); > > /* >- * If the number of nodes in the mask is less than or equal the >+ * If the number of nodes in the mask is greater than or equal the > * number of vectors we just spread the vectors across the nodes. > */ > if (affv <= nodes) {
Thanks, Gavin
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