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Try polling the qpairs on timeout.

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On some systems, we're getting timeouts when we use multiple queues on
drives that work perfectly well on other systems. On a hunch, Jim
Harris suggested I poll the completion queue when we get a timeout.
This patch polls the completion queue if no fatal status was
indicated. If it had pending I/O, we complete that request and
return. Otherwise, if aborts are enabled and no fatal status, we abort
the command and return. Otherwise we reset the card.

This may clear up the problem, or we may see it result in lots of
timeouts and a performance problem. Either way, we'll know the next
step. We may also need to pay attention to the fatal status bit
of the controller.

PR: 211713
Suggested by: Jim Harris
Sponsored by: Netflix
This commit is contained in:
imp 2018-03-16 05:23:48 +00:00
parent f95d03b9ad
commit 0ac2e39d57
2 changed files with 24 additions and 10 deletions
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2
sys/dev/nvme/nvme_private.h
View File

@ -426,7 +426,7 @@ int nvme_qpair_construct(struct nvme_qpair *qpair, uint32_t id,
struct nvme_controller *ctrlr);
void nvme_qpair_submit_tracker(struct nvme_qpair *qpair,
struct nvme_tracker *tr);
void nvme_qpair_process_completions(struct nvme_qpair *qpair);
bool nvme_qpair_process_completions(struct nvme_qpair *qpair);
void nvme_qpair_submit_request(struct nvme_qpair *qpair,
struct nvme_request *req);
void nvme_qpair_reset(struct nvme_qpair *qpair);

32
sys/dev/nvme/nvme_qpair.c
View File

@ -469,11 +469,12 @@ nvme_qpair_manual_complete_request(struct nvme_qpair *qpair,
nvme_free_request(req);
}
void
bool
nvme_qpair_process_completions(struct nvme_qpair *qpair)
{
struct nvme_tracker *tr;
struct nvme_completion cpl;
int done = 0;
qpair->num_intr_handler_calls++;
@ -484,7 +485,7 @@ nvme_qpair_process_completions(struct nvme_qpair *qpair)
* associated with this interrupt will get retried when the
* reset is complete.
*/
return;
return (false);
while (1) {
cpl = qpair->cpl[qpair->cq_head];
@ -500,6 +501,7 @@ nvme_qpair_process_completions(struct nvme_qpair *qpair)
if (tr != NULL) {
nvme_qpair_complete_tracker(qpair, tr, &cpl, TRUE);
qpair->sq_head = cpl.sqhd;
done++;
} else {
nvme_printf(qpair->ctrlr,
"cpl does not map to outstanding cmd\n");
@ -516,6 +518,7 @@ nvme_qpair_process_completions(struct nvme_qpair *qpair)
nvme_mmio_write_4(qpair->ctrlr, doorbell[qpair->id].cq_hdbl,
qpair->cq_head);
}
return (done != 0);
}
static void
@ -770,19 +773,30 @@ nvme_timeout(void *arg)
uint32_t csts;
uint8_t cfs;
/* Read csts to get value of cfs - controller fatal status. */
/*
* Read csts to get value of cfs - controller fatal status.
* If no fatal status, try to call the completion routine, and
* if completes transactions, report a missed interrupt and
* return (this may need to be rate limited). Otherwise, if
* aborts are enabled and the controller is not reporting
* fatal status, abort the command. Otherwise, just reset the
* controller and hope for the best.
*/
csts = nvme_mmio_read_4(ctrlr, csts);
cfs = (csts >> NVME_CSTS_REG_CFS_SHIFT) & NVME_CSTS_REG_CFS_MASK;
if (cfs == 0 && nvme_qpair_process_completions(qpair)) {
nvme_printf(ctrlr, "Missing interrupt\n");
return;
}
if (ctrlr->enable_aborts && cfs == 0) {
/*
* If aborts are enabled, only use them if the controller is
* not reporting fatal status.
*/
nvme_printf(ctrlr, "Aborting command due to a timeout.\n");
nvme_ctrlr_cmd_abort(ctrlr, tr->cid, qpair->id,
nvme_abort_complete, tr);
} else
} else {
nvme_printf(ctrlr, "Resetting controller due to a timeout%s.\n",
cfs ? " and fatal error status" : "");
nvme_ctrlr_reset(ctrlr);
}
}
void