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| alexzzz | Hi! I'm trying to test hybrid polling. Using ubuntu 16.04 with 4.10.0-42-generic kernel (from linux-generic-hwe-16.04 package). When i do echo 0 > /sys/block/sdc/queue/io_poll_delay then i get error: -bash: echo: write error: Invalid argument. I'm logged in as root, so it is not user permissions problem. Did i miss something? | 10:45 |
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| alexzzz | I'm using blk-mq for this disk. scsi_mod.use_blk_mq=y while booting and scheduler for this disk is 'none', which means that scsi_mq is active | 10:48 |
| alexzzz | Any suggestions?:( i really don't know where to look at now | 11:26 |
| juergh | alexzzz, looking | 11:26 |
| alexzzz | juergh: Thak you!:) | 11:26 |
| juergh | if (!q->request_fn && !q->mq_ops) | 11:26 |
| juergh | return -EINVAL; | 11:26 |
| juergh | that's what you're hitting | 11:26 |
| juergh | oh no wait. that's the one: | 11:28 |
| juergh | if (!q->mq_ops || !q->mq_ops->poll) | 11:28 |
| juergh | return -EINVAL; | 11:28 |
| juergh | alexzzz, you need to write 0 to /sys/block/sdc/queue/io_poll first to enable polling (according to the docs). | 11:35 |
| juergh | maeh, make that 'write 1' :-) | 11:35 |
| alexzzz | Hm, but it is 1 | 11:35 |
| juergh | :-( | 11:35 |
| alexzzz | it is a default behavior | 11:35 |
| alexzzz | and i can't turn polling off, echo 0 to io_poll fails with same error invalid argument | 11:36 |
| TJ- | alexzzz: any apparmor denials or other clues in the system logs? | 11:40 |
| alexzzz | TJ-: no, nothing in logs | 11:44 |
| juergh | alexzzz, The low-level driver needs to support IO polling. Currently, only NVME supports it so you're out of luck with a SCSI disk. | 12:05 |
| juergh | $ find drivers/ -type f -name '*.c' | xargs grep -A20 '^static.* struct blk_mq_ops' | grep '\.poll' | 12:05 |
| juergh | drivers/nvme/host/rdma.c-.poll= nvme_rdma_poll, | 12:05 |
| juergh | drivers/nvme/host/pci.c-.poll= nvme_poll, | 12:05 |
| juergh | drivers/nvme/host/fc.c-.poll= nvme_fc_poll, | 12:05 |
| alexzzz | Oh | 12:06 |
| alexzzz | juergh: Thank you very much! | 12:07 |
| juergh | alexzzz, np | 12:07 |
| alexzzz | i will try it on NVMe some time later | 12:07 |
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