From: Yamin Friedman <yaminf@xxxxxxxxxxxx>
Added the interface in the infiniband driver that applies the blk_dim adaptive
moderation.
Performance improvment (ConnectX-5 100GbE, x86) running FIO benchmark over NVMf
between two equal end-hosts across a Mellanox switch:
Running long tests that switch between periods of high bandwidth high latency
and low bandwidth low latency, using the blk_dim algorithm there is a much
shorter wait before the moderation is reduced and thus tail latency is reduced.
There is a 200% reduction on tail latency when switching from high bandwidth to
low bandwidth traffic without degredation of other flow parameters.
The blk_dim algorithm was designed to measure the effectiveness of moderation
on the flow in a general way and thus should be appropriate for all RDMA storage
protocols.
Signed-off-by: Yamin Friedman <yaminf@xxxxxxxxxxxx>
Signed-off-by: Tal Gilboa <talgi@xxxxxxxxxxxx>
---
drivers/infiniband/core/cq.c | 75 ++++++++++++++++++++++++++++++---
drivers/infiniband/hw/mlx4/qp.c | 2 +-
drivers/infiniband/hw/mlx5/qp.c | 2 +-
include/linux/irq_poll.h | 7 +++
include/rdma/ib_verbs.h | 11 ++++-
lib/irq_poll.c | 13 +++++-
6 files changed, 100 insertions(+), 10 deletions(-)
diff --git a/drivers/infiniband/core/cq.c b/drivers/infiniband/core/cq.c
index d61e5e1427c2..065b54978dae 100644
--- a/drivers/infiniband/core/cq.c
+++ b/drivers/infiniband/core/cq.c
@@ -14,6 +14,7 @@
#include <linux/err.h>
#include <linux/slab.h>
#include <rdma/ib_verbs.h>
+#include <linux/blk_dim.h>
/* # of WCs to poll for with a single call to ib_poll_cq */
#define IB_POLL_BATCH 16
@@ -26,6 +27,51 @@
#define IB_POLL_FLAGS \
(IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS)
+static bool use_am = true;
+module_param(use_am, bool, 0444);
+MODULE_PARM_DESC(use_am, "Use cq adaptive moderation");
+
+static int ib_cq_dim_modify_cq(struct ib_cq *cq, unsigned short level)
+{
+ u16 usec = blk_dim_prof[level].usec;
+ u16 comps = blk_dim_prof[level].comps;
+
+ return cq->device->modify_cq(cq, comps, usec);
+}
+
+static void update_cq_moderation(struct dim *dim, struct ib_cq *cq)
+{
+ dim->state = DIM_START_MEASURE;
+
+ ib_cq_dim_modify_cq(cq, dim->profile_ix);
+}
+
+static void ib_cq_blk_dim_workqueue_work(struct work_struct *w)
+{
+ struct dim *dim = container_of(w, struct dim, work);
+ struct ib_cq *cq = container_of(dim, struct ib_cq, workqueue_poll.dim);
+
+ update_cq_moderation(dim, cq);
+}
+
+static void ib_cq_blk_dim_irqpoll_work(struct work_struct *w)
+{
+ struct dim *dim = container_of(w, struct dim, work);
+ struct irq_poll *iop = container_of(dim, struct irq_poll, dim);
+ struct ib_cq *cq = container_of(iop, struct ib_cq, iop);
+
+ update_cq_moderation(dim, cq);
+}
+
+void blk_dim_init(struct dim *dim, work_func_t func)
+{
+ memset(dim, 0, sizeof(*dim));
+ dim->state = DIM_START_MEASURE;
+ dim->tune_state = DIM_GOING_RIGHT;
+ dim->profile_ix = BLK_DIM_START_PROFILE;
+ INIT_WORK(&dim->work, func);
+}
+
static int __ib_process_cq(struct ib_cq *cq, int budget, struct ib_wc *wcs,
int batch)
{
@@ -105,19 +151,28 @@ static void ib_cq_completion_softirq(struct ib_cq *cq, void *private)
static void ib_cq_poll_work(struct work_struct *work)
{
- struct ib_cq *cq = container_of(work, struct ib_cq, work);
+ struct ib_cq *cq = container_of(work, struct ib_cq, workqueue_poll.work);
int completed;
+ struct dim_sample e_sample;
+ struct dim_sample *m_sample = &cq->workqueue_poll.dim.measuring_sample;
completed = __ib_process_cq(cq, IB_POLL_BUDGET_WORKQUEUE, cq->wc,
IB_POLL_BATCH);
+
+ if (cq->workqueue_poll.dim_used)
+ dim_create_sample(m_sample->event_ctr + 1, m_sample->pkt_ctr, m_sample->byte_ctr,
+ m_sample->comp_ctr + completed, &e_sample);
+
if (completed >= IB_POLL_BUDGET_WORKQUEUE ||
ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0)
- queue_work(cq->comp_wq, &cq->work);
+ queue_work(cq->comp_wq, &cq->workqueue_poll.work);
+ else if (cq->workqueue_poll.dim_used)
+ blk_dim(&cq->workqueue_poll.dim, e_sample);
}
static void ib_cq_completion_workqueue(struct ib_cq *cq, void *private)
{
- queue_work(cq->comp_wq, &cq->work);
+ queue_work(cq->comp_wq, &cq->workqueue_poll.work);
}
/**
@@ -172,12 +227,20 @@ struct ib_cq *__ib_alloc_cq(struct ib_device *dev, void *private,
cq->comp_handler = ib_cq_completion_softirq;
irq_poll_init(&cq->iop, IB_POLL_BUDGET_IRQ, ib_poll_handler);
+ if (cq->device->modify_cq && use_am) {
+ blk_dim_init(&cq->iop.dim, ib_cq_blk_dim_irqpoll_work);
+ cq->iop.dim_used = true;
+ }
ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
break;
case IB_POLL_WORKQUEUE:
case IB_POLL_UNBOUND_WORKQUEUE:
cq->comp_handler = ib_cq_completion_workqueue;
- INIT_WORK(&cq->work, ib_cq_poll_work);
+ INIT_WORK(&cq->workqueue_poll.work, ib_cq_poll_work);
+ if (cq->device->modify_cq && use_am) {
+ blk_dim_init(&cq->workqueue_poll.dim, ib_cq_blk_dim_workqueue_work);
+ cq->workqueue_poll.dim_used = true;
+ }
ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
cq->comp_wq = (cq->poll_ctx == IB_POLL_WORKQUEUE) ?
ib_comp_wq : ib_comp_unbound_wq;
@@ -217,7 +280,9 @@ void ib_free_cq(struct ib_cq *cq)
break;
case IB_POLL_WORKQUEUE:
case IB_POLL_UNBOUND_WORKQUEUE:
- cancel_work_sync(&cq->work);
+ cancel_work_sync(&cq->workqueue_poll.work);
+ if (cq->workqueue_poll.dim_used)
+ flush_work(&cq->iop.dim.work);
break;
default:
WARN_ON_ONCE(1);
diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index 971e9a9ebdaf..f3e5dbe4689a 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -4365,7 +4365,7 @@ static void handle_drain_completion(struct ib_cq *cq,
irq_poll_enable(&cq->iop);
break;
case IB_POLL_WORKQUEUE:
- cancel_work_sync(&cq->work);
+ cancel_work_sync(&cq->workqueue_poll.work);
break;
default:
WARN_ON_ONCE(1);
diff --git a/drivers/infiniband/hw/mlx5/qp.c b/drivers/infiniband/hw/mlx5/qp.c
index dd2ae640bc84..4b65147010cc 100644
--- a/drivers/infiniband/hw/mlx5/qp.c
+++ b/drivers/infiniband/hw/mlx5/qp.c
@@ -6102,7 +6102,7 @@ static void handle_drain_completion(struct ib_cq *cq,
irq_poll_enable(&cq->iop);
break;
case IB_POLL_WORKQUEUE:
- cancel_work_sync(&cq->work);
+ cancel_work_sync(&cq->workqueue_poll.work);
break;
default:
WARN_ON_ONCE(1);
diff --git a/include/linux/irq_poll.h b/include/linux/irq_poll.h
index 16aaeccb65cb..ede1a390159b 100644
--- a/include/linux/irq_poll.h
+++ b/include/linux/irq_poll.h
@@ -2,14 +2,21 @@
#ifndef IRQ_POLL_H
#define IRQ_POLL_H
+#include <linux/blk_dim.h>
+
struct irq_poll;
typedef int (irq_poll_fn)(struct irq_poll *, int);
+typedef int (irq_poll_dim_fn)(struct irq_poll *);
struct irq_poll {
struct list_head list;
unsigned long state;
int weight;
irq_poll_fn *poll;
+
+ bool dim_used;
+ struct dim dim;
+ irq_poll_dim_fn *dimfn;
};
enum {
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index a3ceed3a040a..d8060c3cee06 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1584,6 +1584,13 @@ enum ib_poll_context {
IB_POLL_UNBOUND_WORKQUEUE, /* poll from unbound workqueue */
};
+struct ib_cq_workqueue_poll {
+ struct dim dim;
+ struct work_struct work;
+ bool dim_used;
+};
+
+
struct ib_cq {
struct ib_device *device;
struct ib_uobject *uobject;
@@ -1595,8 +1602,8 @@ struct ib_cq {
enum ib_poll_context poll_ctx;
struct ib_wc *wc;
union {
- struct irq_poll iop;
- struct work_struct work;
+ struct irq_poll iop;
+ struct ib_cq_workqueue_poll workqueue_poll;
};
struct workqueue_struct *comp_wq;
/*
diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 86a709954f5a..2b5e41f0e583 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -53,6 +53,8 @@ static void __irq_poll_complete(struct irq_poll *iop)
list_del(&iop->list);
smp_mb__before_atomic();
clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
+ if (iop->dim_used)
+ blk_dim(&iop->dim, iop->dim.measuring_sample);
}
/**
@@ -86,6 +88,7 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
while (!list_empty(list)) {
struct irq_poll *iop;
int work, weight;
+ struct dim_sample *m_sample;
/*
* If softirq window is exhausted then punt.
@@ -104,10 +107,16 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
*/
iop = list_entry(list->next, struct irq_poll, list);
+ m_sample = &iop->dim.measuring_sample;
weight = iop->weight;
work = 0;
- if (test_bit(IRQ_POLL_F_SCHED, &iop->state))
+ if (test_bit(IRQ_POLL_F_SCHED, &iop->state)) {
work = iop->poll(iop, weight);
+ if (iop->dim_used)
+ dim_create_sample(m_sample->event_ctr + 1, m_sample->pkt_ctr,
+ m_sample->byte_ctr, m_sample->comp_ctr + work,
+ &iop->dim.measuring_sample);
+ }
budget -= work;
@@ -144,6 +153,8 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
**/
void irq_poll_disable(struct irq_poll *iop)
{
+ if (iop->dim_used)
+ flush_work(&iop->dim.work);
set_bit(IRQ_POLL_F_DISABLE, &iop->state);
while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
msleep(1);
--
2.19.1
