On Thu, Sep 19, 2019 at 01:47:50PM +0000, Bharat Kumar Gogada wrote:
> Hi All,
>
> We are testing NVMe cards on ARM64 platform, the card uses MSI-X interrupts.
> We are hitting following case in drivers/nvme/host/pci.c
> /*
> * Did we miss an interrupt?
> */
> if (__nvme_poll(nvmeq, req->tag)) {
> dev_warn(dev->ctrl.device,
> "I/O %d QID %d timeout, completion polled\n",
> req->tag, nvmeq->qid);
> return BLK_EH_DONE;
> }
>
> Can anyone tell when does nvme_timeout gets invoked ?
Timeout is invoked when the driver didn't see a completion to a
submitted command.
> In what cases we see this interrupt miss ?
That usually happens for one of two reasons:
1. The device didn't send any MSIx message for a CQE
2. The device sent the MSIx message before posting the CQE
I've also seen h/w errata where the MSIx and CQE are re-ordered, which
can also lead to this.
A hardware trace would provide the most detailed view of what's
happening. You might be able to infer if you carefully account for
commands sent, interrupts received, and spurious interrupts detected.
> We are seeing this issue only for reads with following fio command
> fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=randread --bs=128k
> --direct=0 \
> --size=128M --numjobs=3 --group_reporting --filename=/dev/nvme0n1
>
> We are not seeing issue with --rw=randwrite for same size.
>
> Please let us know what can cause this issue.
