diff options
author | Uday Shankar <ushankar@purestorage.com> | 2023-05-25 21:22:04 +0300 |
---|---|---|
committer | Keith Busch <kbusch@kernel.org> | 2023-05-31 06:57:42 +0300 |
commit | c7275ce6a5fd32ca9f5a6294ed89cf0523181af9 (patch) | |
tree | 9751bb1f78691a18d83a3a84aa5f84cb052397b4 /drivers/nvme | |
parent | 774a9636514764ddc0d072ae0d1d1c01a47e6ddd (diff) | |
download | linux-c7275ce6a5fd32ca9f5a6294ed89cf0523181af9.tar.xz |
nvme: improve handling of long keep alives
Upon keep alive completion, nvme_keep_alive_work is scheduled with the
same delay every time. If keep alive commands are completing slowly,
this may cause a keep alive timeout. The following trace illustrates the
issue, taking KATO = 8 and TBKAS off for simplicity:
1. t = 0: run nvme_keep_alive_work, send keep alive
2. t = ε: keep alive reaches controller, controller restarts its keep
alive timer
3. t = 4: host receives keep alive completion, schedules
nvme_keep_alive_work with delay 4
4. t = 8: run nvme_keep_alive_work, send keep alive
Here, a keep alive having RTT of 4 causes a delay of at least 8 - ε
between the controller receiving successive keep alives. With ε small,
the controller is likely to detect a keep alive timeout.
Fix this by calculating the RTT of the keep alive command, and adjusting
the scheduling delay of the next keep alive work accordingly.
Reported-by: Costa Sapuntzakis <costa@purestorage.com>
Reported-by: Randy Jennings <randyj@purestorage.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Diffstat (limited to 'drivers/nvme')
-rw-r--r-- | drivers/nvme/host/core.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index dbfca1b925f8..3ec38e2b9173 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -1199,6 +1199,20 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, struct nvme_ctrl *ctrl = rq->end_io_data; unsigned long flags; bool startka = false; + unsigned long rtt = jiffies - (rq->deadline - rq->timeout); + unsigned long delay = nvme_keep_alive_work_period(ctrl); + + /* + * Subtract off the keepalive RTT so nvme_keep_alive_work runs + * at the desired frequency. + */ + if (rtt <= delay) { + delay -= rtt; + } else { + dev_warn(ctrl->device, "long keepalive RTT (%u ms)\n", + jiffies_to_msecs(rtt)); + delay = 0; + } blk_mq_free_request(rq); @@ -1217,7 +1231,7 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, startka = true; spin_unlock_irqrestore(&ctrl->lock, flags); if (startka) - nvme_queue_keep_alive_work(ctrl); + queue_delayed_work(nvme_wq, &ctrl->ka_work, delay); return RQ_END_IO_NONE; } |