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SubjectRe: [PATCH] irq: consider cpus on nodes are unbalanced
Date
On Wed, Nov 24 2021 at 20:33, Thomas Gleixner wrote:
> Cc'ing a few people who worked on this code.
>
>> If cpus on a node are offline at boot time, there are
>> difference in the number of nodes between when building affinity
>> masks for present cpus and when building affinity masks for possible
>> cpus. This patch fixes 2 problems caused by the difference of the
>> number of nodes:
>>
>> - If some unused vectors remain after building masks for present cpus,
>> remained vectors are assigned for building masks for possible cpus.
>> Therefore "numvecs <= nodes" condition must be
>> "vecs_to_assign <= nodes_to_assign". Fix this problem by making this
>> condition appropriate.
>>
>> - The routine of "numvecs <= nodes" condition can overwrite bits of
>> masks for present cpus in building masks for possible cpus. Fix this
>> problem by making CPU bits, which is not target, not changing.
>>
>> Signed-off-by: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
>> ---
>> kernel/irq/affinity.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
>> index f7ff8919dc9b..1cdf89e5e2fb 100644
>> --- a/kernel/irq/affinity.c
>> +++ b/kernel/irq/affinity.c
>> @@ -267,10 +267,16 @@ static int __irq_build_affinity_masks(unsigned int startvec,
>> * 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 (numvecs <= nodes) {
>> + if (numvecs - (curvec - firstvec) <= nodes) {
>> for_each_node_mask(n, nodemsk) {
>> + unsigned int ncpus;
>> +
>> + cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
>> + ncpus = cpumask_weight(nmsk);
>> + if (!ncpus)
>> + continue;
>> cpumask_or(&masks[curvec].mask, &masks[curvec].mask,
>> - node_to_cpumask[n]);
>> + nmsk);
>> if (++curvec == last_affv)
>> curvec = firstvec;
>> }

Do you have any comments?

Rei

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