Messages in this thread | | | Date | Thu, 19 Sep 2019 08:13:01 -0600 | From | Keith Busch <> | Subject | Re: NVMe Poll CQ on timeout |
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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.
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