Independent from the issues with the dasd disks, this also seem to not enable
additional hardware queues.
with cpus 0,1 (and 248 cpus max)
I get cpus 0 and 2-247 attached to hardware contect 0 and I get
cpu 1 for hardware context 1.
If I now add a cpu this does not change anything. hardware context 2,3,4
etc all have no CPU and hardware context 0 keeps sitting on all cpus (except 1).
On 12/07/2017 10:20 AM, Christian Borntraeger wrote:
>
>
> On 12/07/2017 12:29 AM, Christoph Hellwig wrote:
>> On Wed, Dec 06, 2017 at 01:25:11PM +0100, Christian Borntraeger wrote:
>> t > commit 11b2025c3326f7096ceb588c3117c7883850c068 -> bad
>>> blk-mq: create a blk_mq_ctx for each possible CPU
>>> does not boot on DASD and
>>> commit 9c6ae239e01ae9a9f8657f05c55c4372e9fc8bcc -> good
>>> genirq/affinity: assign vectors to all possible CPUs
>>> does boot with DASD disks.
>>>
>>> Also adding Stefan Haberland if he has an idea why this fails on DASD and adding Martin (for the
>>> s390 irq handling code).
>>
>> That is interesting as it really isn't related to interrupts at all,
>> it just ensures that possible CPUs are set in ->cpumask.
>>
>> I guess we'd really want:
>>
>> e005655c389e3d25bf3e43f71611ec12f3012de0
>> "blk-mq: only select online CPUs in blk_mq_hctx_next_cpu"
>>
>> before this commit, but it seems like the whole stack didn't work for
>> your either.
>>
>> I wonder if there is some weird thing about nr_cpu_ids in s390?
>
> The problem starts as soon as NR_CPUS is larger than the number
> of real CPUs.
>
> Aquestions Wouldnt your change in blk_mq_hctx_next_cpu fail if there is more than 1 non-online cpu:
>
> e.g. dont we need something like (whitespace and indent damaged)
>
> @@ -1241,11 +1241,11 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
> if (--hctx->next_cpu_batch <= 0) {
> int next_cpu;
>
> + do {
> next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
> - if (!cpu_online(next_cpu))
> - next_cpu = cpumask_next(next_cpu, hctx->cpumask);
> if (next_cpu >= nr_cpu_ids)
> next_cpu = cpumask_first(hctx->cpumask);
> + } while (!cpu_online(next_cpu));
>
> hctx->next_cpu = next_cpu;
> hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
>
> it does not fix the issue, though (and it would be pretty inefficient for large NR_CPUS)
>
>
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