[PATCH v3 0/4] traffic based keep alive support (TP 4024)

[PATCH v3 0/4] traffic based keep alive support (TP 4024)

[Sagi Grimberg]

Traffic Based Keep Alive TP (4024) was ratified recently. The technical
proposal introduces a mode where keep alive commands may be omitted
based on the presence of admin or io traffic during the keep alive timeout
period. The rational is that normal command execution is sufficient
indication of host, controller and transport health so the keep alive command
is redundant.

Moreover, There is no way to guarantee in the various transports that a
keep alive command will not be starved by heavy traffic, causing the
keep alive timeout to expire. There were a number bug reports on
linux nvme community on this exact issue.

The implementation simply a controller-wide indicator that is cleared
upon reset of the keep alive timer and set when a command (target) or
completion (host) is processed. When the keep alive timer expires, we
check if any command/completion were processed, we restart the keep
alive timer even if a keep alive command was not executed.

Changes from v2:
- fixed debug messages for traffic based keep alive
- collected review tags

Changes from v1:
- omit comp_seen update for controllers that don't support keep alive

Sagi Grimberg (4):
  nvme: introduce ctrl attributes enumeration
  nvmet: support for traffic based keep-alive
  nvme-core: cache controller attributes
  nvme-core: support traffic based keep-alive based on controller
    support

 drivers/nvme/host/core.c        | 14 ++++++++++++++
 drivers/nvme/host/nvme.h        |  2 ++
 drivers/nvme/target/admin-cmd.c |  3 ++-
 drivers/nvme/target/core.c      | 12 ++++++++++++
 drivers/nvme/target/nvmet.h     |  2 ++
 include/linux/nvme.h            |  5 +++++
 6 files changed, 37 insertions(+), 1 deletion(-)

-- 
2.17.1

[PATCH v3 1/4] nvme: introduce ctrl attributes enumeration

[Sagi Grimberg]

We are growing more controller attributes, so use
a proper enumeration for it. For now just add the
128-bit hostid which we support.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
Reviewed-by: Hannes Reinecke <hare at suse.com>
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/target/admin-cmd.c | 2 +-
 include/linux/nvme.h            | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 1179f6314323..30778ffc46f5 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -304,7 +304,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 
 	/* XXX: figure out what to do about RTD3R/RTD3 */
 	id->oaes = cpu_to_le32(NVMET_AEN_CFG_OPTIONAL);
-	id->ctratt = cpu_to_le32(1 << 0);
+	id->ctratt = cpu_to_le32(NVME_CTRL_ATTR_HID_128_BIT);
 
 	id->oacs = 0;
 
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 818dbe9331be..753c83a5c01f 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -198,6 +198,10 @@ enum {
 	NVME_PS_FLAGS_NON_OP_STATE	= 1 << 1,
 };
 
+enum nvme_ctrl_attr {
+	NVME_CTRL_ATTR_HID_128_BIT	= (1 << 0),
+};
+
 struct nvme_id_ctrl {
 	__le16			vid;
 	__le16			ssvid;
-- 
2.17.1

[PATCH v3 2/4] nvmet: support for traffic based keep-alive

[Sagi Grimberg]

A controller that supports traffic based keep-alive can restart
its keep alive timer even if keep-alive was not issued in the
kato period but other admin or io commands was. For each command
set ctrl->cmd_seen to true, and when keep-alive timer expires,
if any commands were seen, resched ka_work instead of escalating
to a fatal error.

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/target/admin-cmd.c |  3 ++-
 drivers/nvme/target/core.c      | 12 ++++++++++++
 drivers/nvme/target/nvmet.h     |  2 ++
 include/linux/nvme.h            |  1 +
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 30778ffc46f5..c9c6d25a3ec2 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -304,7 +304,8 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 
 	/* XXX: figure out what to do about RTD3R/RTD3 */
 	id->oaes = cpu_to_le32(NVMET_AEN_CFG_OPTIONAL);
-	id->ctratt = cpu_to_le32(NVME_CTRL_ATTR_HID_128_BIT);
+	id->ctratt = cpu_to_le32(NVME_CTRL_ATTR_HID_128_BIT |
+		NVME_CTRL_ATTR_TBKAS);
 
 	id->oacs = 0;
 
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 0acdff9e6842..b9fbb60921a4 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -298,6 +298,15 @@ static void nvmet_keep_alive_timer(struct work_struct *work)
 {
 	struct nvmet_ctrl *ctrl = container_of(to_delayed_work(work),
 			struct nvmet_ctrl, ka_work);
+	bool cmd_seen = ctrl->cmd_seen;
+
+	ctrl->cmd_seen = false;
+	if (cmd_seen) {
+		pr_debug("ctrl %d reschedule traffic based keep-alive timer\n",
+			ctrl->cntlid);
+		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+		return;
+	}
 
 	pr_err("ctrl %d keep-alive timer (%d seconds) expired!\n",
 		ctrl->cntlid, ctrl->kato);
@@ -700,6 +709,9 @@ bool nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
 		goto fail;
 	}
 
+	if (sq->ctrl)
+		sq->ctrl->cmd_seen = true;
+
 	return true;
 
 fail:
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 08f7b57a1203..c5255e743f63 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -154,6 +154,8 @@ struct nvmet_ctrl {
 	struct nvmet_cq		**cqs;
 	struct nvmet_sq		**sqs;
 
+	bool			cmd_seen;
+
 	struct mutex		lock;
 	u64			cap;
 	u32			cc;
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 753c83a5c01f..429c4cf90899 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -200,6 +200,7 @@ enum {
 
 enum nvme_ctrl_attr {
 	NVME_CTRL_ATTR_HID_128_BIT	= (1 << 0),
+	NVME_CTRL_ATTR_TBKAS		= (1 << 6),
 };
 
 struct nvme_id_ctrl {
-- 
2.17.1

[PATCH v3 3/4] nvme-core: cache controller attributes

[Sagi Grimberg]

We get the controller attributes in identify, cache
them as we'll need them for traffic based keep alive
support.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/core.c | 1 +
 drivers/nvme/host/nvme.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 65c42448e904..ef609239c9c5 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2409,6 +2409,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	ctrl->sgls = le32_to_cpu(id->sgls);
 	ctrl->kas = le16_to_cpu(id->kas);
 	ctrl->max_namespaces = le32_to_cpu(id->mnan);
+	ctrl->ctratt = le32_to_cpu(id->ctratt);
 
 	if (id->rtd3e) {
 		/* us -> s */
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 9fefba039d1e..4dd7535caf1b 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -193,6 +193,7 @@ struct nvme_ctrl {
 	u8 apsta;
 	u32 oaes;
 	u32 aen_result;
+	u32 ctratt;
 	unsigned int shutdown_timeout;
 	unsigned int kato;
 	bool subsystem;
-- 
2.17.1

[PATCH v3 4/4] nvme-core: support traffic based keep-alive based on controller support

[Sagi Grimberg]

If the controller supports traffic based keep alive, we restart
the keep alive timer if any admin or io commands was completed
during the kato period. This prevents a possible starvation of
keep alive commands in the presence of heavy traffic as in such
case, we already have a health indication from the host perspective.

Only set a comp_seen indicator in case the controller supports keep
alive to minimize the overhead for pci controllers.

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/core.c | 13 +++++++++++++
 drivers/nvme/host/nvme.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ef609239c9c5..a24e3321828d 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -251,6 +251,9 @@ void nvme_complete_rq(struct request *req)
 
 	trace_nvme_complete_rq(req);
 
+	if (nvme_req(req)->ctrl->kas)
+		nvme_req(req)->ctrl->comp_seen = true;
+
 	if (unlikely(status != BLK_STS_OK && nvme_req_needs_retry(req))) {
 		if ((req->cmd_flags & REQ_NVME_MPATH) &&
 		    blk_path_error(status)) {
@@ -841,6 +844,7 @@ static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 		return;
 	}
 
+	ctrl->comp_seen = false;
 	schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
 }
 
@@ -865,6 +869,15 @@ static void nvme_keep_alive_work(struct work_struct *work)
 {
 	struct nvme_ctrl *ctrl = container_of(to_delayed_work(work),
 			struct nvme_ctrl, ka_work);
+	bool comp_seen = ctrl->comp_seen;
+
+	if ((ctrl->ctratt & NVME_CTRL_ATTR_TBKAS) && comp_seen) {
+		dev_dbg(ctrl->device,
+			"reschedule traffic based keep-alive timer\n");
+		ctrl->comp_seen = false;
+		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+		return;
+	}
 
 	if (nvme_keep_alive(ctrl)) {
 		/* allocation failure, reset the controller */
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 4dd7535caf1b..6206d026d53b 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -145,6 +145,7 @@ enum nvme_ctrl_state {
 };
 
 struct nvme_ctrl {
+	bool comp_seen;
 	enum nvme_ctrl_state state;
 	bool identified;
 	spinlock_t lock;
-- 
2.17.1

[PATCH v3 0/4] traffic based keep alive support (TP 4024)

[Christoph Hellwig]

Thanks,

applied to nvme-4.21.