On 04/06/2018 11:23 AM, Ming Lei wrote: > On Fri, Apr 06, 2018 at 10:51:28AM +0200, Christian Borntraeger wrote: >> >> >> On 04/06/2018 10:41 AM, Ming Lei wrote: >>> On Thu, Apr 05, 2018 at 07:39:56PM +0200, Christian Borntraeger wrote: >>>> >>>> >>>> On 04/05/2018 06:11 PM, Ming Lei wrote: >>>>>> >>>>>> Could you please apply the following patch and provide the dmesg boot log? >>>>> >>>>> And please post out the 'lscpu' log together from the test machine too. >>>> >>>> attached. >>>> >>>> As I said before this seems to go way with CONFIG_NR_CPUS=64 or smaller. >>>> We have 282 nr_cpu_ids here (max 141CPUs on that z13 with SMT2) but only 8 Cores >>>> == 16 threads. >>> >>> OK, thanks! >>> >>> The most weird thing is that hctx->next_cpu is computed as 512 since >>> nr_cpu_id is 282, and hctx->next_cpu should have pointed to one of >>> possible CPU. >>> >>> Looks like it is a s390 specific issue, since I can setup one queue >>> which has same mapping with yours: >>> >>> - nr_cpu_id is 282 >>> - CPU 0~15 is online >>> - 64 queues null_blk >>> - still run all hw queues in .complete handler >>> >>> But can't reproduce this issue at all. >>> >>> So please test the following patch, which may tell us why hctx->next_cpu >>> is computed wrong: >> >> I see things like >> >> [ 8.196907] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196910] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196912] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196913] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196914] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196915] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196916] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196916] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196917] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> [ 8.196918] wrong next_cpu 512, blk_mq_map_swqueue, first_and >> >> which is exactly what happens if the find and and operation fails (returns size of bitmap). > > Given both 'cpu_online_mask' and 'hctx->cpumask' are shown as correct > in your previous debug log, it means the following function returns > totally wrong result on S390. > > cpumask_first_and(hctx->cpumask, cpu_online_mask); > > The debugfs log shows that each hctx->cpumask includes one online > CPU(0~15). Really? the last log (with the latest patch applied shows a lot of contexts that do not have CPUs in 0-15: e.g. [ 4.049828] dump CPUs mapped to this hctx: [ 4.049829] 18 [ 4.049829] 82 [ 4.049830] 146 [ 4.049830] 210 [ 4.049831] 274 > > So looks it isn't one issue in block MQ core. > > Thanks, > Ming >
