net/mlx5: CQ Database per EQ

Before this patch the driver had one CQ database protected via one
spinlock, this spinlock is meant to synchronize between CQ
adding/removing and CQ IRQ interrupt handling.

On a system with large number of CPUs and on a work load that requires
lots of interrupts, this global spinlock becomes a very nasty hotspot
and introduces a contention between the active cores, which will
significantly hurt performance and becomes a bottleneck that prevents
seamless cpu scaling.

To solve this we simply move the CQ database and its spinlock to be per
EQ (IRQ), thus per core.

Tested with:
system: 2 sockets, 14 cores per socket, hyperthreading, 2x14x2=56 cores
netperf command: ./super_netperf 200 -P 0 -t TCP_RR  -H <server> -l 30 -- -r 300,300 -o -s 1M,1M -S 1M,1M

WITHOUT THIS PATCH:
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft %steal  %guest  %gnice   %idle
Average:     all    4.32    0.00   36.15    0.09    0.00   34.02   0.00    0.00    0.00   25.41

Samples: 2M of event 'cycles:pp', Event count (approx.): 1554616897271
Overhead  Command          Shared Object                 Symbol
+   14.28%  swapper          [kernel.vmlinux]              [k] intel_idle
+   12.25%  swapper          [kernel.vmlinux]              [k] queued_spin_lock_slowpath
+   10.29%  netserver        [kernel.vmlinux]              [k] queued_spin_lock_slowpath
+    1.32%  netserver        [kernel.vmlinux]              [k] mlx5e_xmit

WITH THIS PATCH:
Average:     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
Average:     all    4.27    0.00   34.31    0.01    0.00   18.71    0.00    0.00    0.00   42.69

Samples: 2M of event 'cycles:pp', Event count (approx.): 1498132937483
Overhead  Command          Shared Object             Symbol
+   23.33%  swapper          [kernel.vmlinux]          [k] intel_idle
+    1.69%  netserver        [kernel.vmlinux]          [k] mlx5e_xmit
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Gal Pressman <galp@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/cq.c

@@ -86,10 +86,10 @@ static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq)
 	spin_unlock_irqrestore(&tasklet_ctx->lock, flags);
 }
 
-void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn)
+void mlx5_cq_completion(struct mlx5_eq *eq, u32 cqn)
 {
+	struct mlx5_cq_table *table = &eq->cq_table;
 	struct mlx5_core_cq *cq;
-	struct mlx5_cq_table *table = &dev->priv.cq_table;
 
 	spin_lock(&table->lock);
 	cq = radix_tree_lookup(&table->tree, cqn);
@@ -98,7 +98,7 @@ void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn)
 	spin_unlock(&table->lock);
 
 	if (!cq) {
-		mlx5_core_warn(dev, "Completion event for bogus CQ 0x%x\n", cqn);
+		mlx5_core_warn(eq->dev, "Completion event for bogus CQ 0x%x\n", cqn);
 		return;
 	}
 
@@ -110,9 +110,9 @@ void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn)
 		complete(&cq->free);
 }
 
-void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type)
+void mlx5_cq_event(struct mlx5_eq *eq, u32 cqn, int event_type)
 {
-	struct mlx5_cq_table *table = &dev->priv.cq_table;
+	struct mlx5_cq_table *table = &eq->cq_table;
 	struct mlx5_core_cq *cq;
 
 	spin_lock(&table->lock);
@@ -124,7 +124,7 @@ void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type)
 	spin_unlock(&table->lock);
 
 	if (!cq) {
-		mlx5_core_warn(dev, "Async event for bogus CQ 0x%x\n", cqn);
+		mlx5_core_warn(eq->dev, "Async event for bogus CQ 0x%x\n", cqn);
 		return;
 	}
 
@@ -137,19 +137,22 @@ void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type)
 int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
 			u32 *in, int inlen)
 {
-	struct mlx5_cq_table *table = &dev->priv.cq_table;
 	u32 out[MLX5_ST_SZ_DW(create_cq_out)];
 	u32 din[MLX5_ST_SZ_DW(destroy_cq_in)];
 	u32 dout[MLX5_ST_SZ_DW(destroy_cq_out)];
 	int eqn = MLX5_GET(cqc, MLX5_ADDR_OF(create_cq_in, in, cq_context),
 			   c_eqn);
-	struct mlx5_eq *eq;
+	struct mlx5_eq *eq, *async_eq;
+	struct mlx5_cq_table *table;
 	int err;
 
+	async_eq = &dev->priv.eq_table.async_eq;
 	eq = mlx5_eqn2eq(dev, eqn);
 	if (IS_ERR(eq))
 		return PTR_ERR(eq);
 
+	table = &eq->cq_table;
+
 	memset(out, 0, sizeof(out));
 	MLX5_SET(create_cq_in, in, opcode, MLX5_CMD_OP_CREATE_CQ);
 	err = mlx5_cmd_exec(dev, in, inlen, out, sizeof(out));
@@ -159,6 +162,7 @@ int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
 	cq->cqn = MLX5_GET(create_cq_out, out, cqn);
 	cq->cons_index = 0;
 	cq->arm_sn     = 0;
+	cq->eq         = eq;
 	refcount_set(&cq->refcount, 1);
 	init_completion(&cq->free);
 	if (!cq->comp)
@@ -167,12 +171,20 @@ int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
 	cq->tasklet_ctx.priv = &eq->tasklet_ctx;
 	INIT_LIST_HEAD(&cq->tasklet_ctx.list);
 
+	/* Add to comp EQ CQ tree to recv comp events */
 	spin_lock_irq(&table->lock);
 	err = radix_tree_insert(&table->tree, cq->cqn, cq);
 	spin_unlock_irq(&table->lock);
 	if (err)
 		goto err_cmd;
 
+	/* Add to async EQ CQ tree to recv Async events */
+	spin_lock_irq(&async_eq->cq_table.lock);
+	err = radix_tree_insert(&async_eq->cq_table.tree, cq->cqn, cq);
+	spin_unlock_irq(&async_eq->cq_table.lock);
+	if (err)
+		goto err_cq_table;
+
 	cq->pid = current->pid;
 	err = mlx5_debug_cq_add(dev, cq);
 	if (err)
@@ -183,6 +195,10 @@ int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
 
 	return 0;
 
+err_cq_table:
+	spin_lock_irq(&table->lock);
+	radix_tree_delete(&table->tree, cq->cqn);
+	spin_unlock_irq(&table->lock);
 err_cmd:
 	memset(din, 0, sizeof(din));
 	memset(dout, 0, sizeof(dout));
@@ -195,21 +211,34 @@ EXPORT_SYMBOL(mlx5_core_create_cq);
 
 int mlx5_core_destroy_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq)
 {
-	struct mlx5_cq_table *table = &dev->priv.cq_table;
+	struct mlx5_cq_table *asyn_eq_cq_table = &dev->priv.eq_table.async_eq.cq_table;
+	struct mlx5_cq_table *table = &cq->eq->cq_table;
 	u32 out[MLX5_ST_SZ_DW(destroy_cq_out)] = {0};
 	u32 in[MLX5_ST_SZ_DW(destroy_cq_in)] = {0};
 	struct mlx5_core_cq *tmp;
 	int err;
 
+	spin_lock_irq(&asyn_eq_cq_table->lock);
+	tmp = radix_tree_delete(&asyn_eq_cq_table->tree, cq->cqn);
+	spin_unlock_irq(&asyn_eq_cq_table->lock);
+	if (!tmp) {
+		mlx5_core_warn(dev, "cq 0x%x not found in async eq cq tree\n", cq->cqn);
+		return -EINVAL;
+	}
+	if (tmp != cq) {
+		mlx5_core_warn(dev, "corruption on cqn 0x%x in async eq cq tree\n", cq->cqn);
+		return -EINVAL;
+	}
+
 	spin_lock_irq(&table->lock);
 	tmp = radix_tree_delete(&table->tree, cq->cqn);
 	spin_unlock_irq(&table->lock);
 	if (!tmp) {
-		mlx5_core_warn(dev, "cq 0x%x not found in tree\n", cq->cqn);
+		mlx5_core_warn(dev, "cq 0x%x not found in comp eq cq tree\n", cq->cqn);
 		return -EINVAL;
 	}
 	if (tmp != cq) {
-		mlx5_core_warn(dev, "corruption on srqn 0x%x\n", cq->cqn);
+		mlx5_core_warn(dev, "corruption on cqn 0x%x in comp eq cq tree\n", cq->cqn);
 		return -EINVAL;
 	}
 
@@ -270,21 +299,3 @@ int mlx5_core_modify_cq_moderation(struct mlx5_core_dev *dev,
 	return mlx5_core_modify_cq(dev, cq, in, sizeof(in));
 }
 EXPORT_SYMBOL(mlx5_core_modify_cq_moderation);
-
-int mlx5_init_cq_table(struct mlx5_core_dev *dev)
-{
-	struct mlx5_cq_table *table = &dev->priv.cq_table;
-	int err;
-
-	memset(table, 0, sizeof(*table));
-	spin_lock_init(&table->lock);
-	INIT_RADIX_TREE(&table->tree, GFP_ATOMIC);
-	err = mlx5_cq_debugfs_init(dev);
-
-	return err;
-}
-
-void mlx5_cleanup_cq_table(struct mlx5_core_dev *dev)
-{
-	mlx5_cq_debugfs_cleanup(dev);
-}

drivers/net/ethernet/mellanox/mlx5/core/eq.c

@@ -415,7 +415,7 @@ static irqreturn_t mlx5_eq_int(int irq, void *eq_ptr)
 		switch (eqe->type) {
 		case MLX5_EVENT_TYPE_COMP:
 			cqn = be32_to_cpu(eqe->data.comp.cqn) & 0xffffff;
-			mlx5_cq_completion(dev, cqn);
+			mlx5_cq_completion(eq, cqn);
 			break;
 		case MLX5_EVENT_TYPE_DCT_DRAINED:
 			rsn = be32_to_cpu(eqe->data.dct.dctn) & 0xffffff;
@@ -472,7 +472,7 @@ static irqreturn_t mlx5_eq_int(int irq, void *eq_ptr)
 			cqn = be32_to_cpu(eqe->data.cq_err.cqn) & 0xffffff;
 			mlx5_core_warn(dev, "CQ error on CQN 0x%x, syndrome 0x%x\n",
 				       cqn, eqe->data.cq_err.syndrome);
-			mlx5_cq_event(dev, cqn, eqe->type);
+			mlx5_cq_event(eq, cqn, eqe->type);
 			break;
 
 		case MLX5_EVENT_TYPE_PAGE_REQUEST:
@@ -567,6 +567,7 @@ int mlx5_create_map_eq(struct mlx5_core_dev *dev, struct mlx5_eq *eq, u8 vecidx,
 		       int nent, u64 mask, const char *name,
 		       enum mlx5_eq_type type)
 {
+	struct mlx5_cq_table *cq_table = &eq->cq_table;
 	u32 out[MLX5_ST_SZ_DW(create_eq_out)] = {0};
 	struct mlx5_priv *priv = &dev->priv;
 	irq_handler_t handler;
@@ -576,6 +577,11 @@ int mlx5_create_map_eq(struct mlx5_core_dev *dev, struct mlx5_eq *eq, u8 vecidx,
 	u32 *in;
 	int err;
 
+	/* Init CQ table */
+	memset(cq_table, 0, sizeof(*cq_table));
+	spin_lock_init(&cq_table->lock);
+	INIT_RADIX_TREE(&cq_table->tree, GFP_ATOMIC);
+
 	eq->type = type;
 	eq->nent = roundup_pow_of_two(nent + MLX5_NUM_SPARE_EQE);
 	eq->cons_index = 0;

drivers/net/ethernet/mellanox/mlx5/core/main.c

@@ -942,9 +942,9 @@ static int mlx5_init_once(struct mlx5_core_dev *dev, struct mlx5_priv *priv)
 		goto out;
 	}
 
-	err = mlx5_init_cq_table(dev);
+	err = mlx5_cq_debugfs_init(dev);
 	if (err) {
-		dev_err(&pdev->dev, "failed to initialize cq table\n");
+		dev_err(&pdev->dev, "failed to initialize cq debugfs\n");
 		goto err_eq_cleanup;
 	}
 
@@ -1002,7 +1002,7 @@ static int mlx5_init_once(struct mlx5_core_dev *dev, struct mlx5_priv *priv)
 	mlx5_cleanup_mkey_table(dev);
 	mlx5_cleanup_srq_table(dev);
 	mlx5_cleanup_qp_table(dev);
-	mlx5_cleanup_cq_table(dev);
+	mlx5_cq_debugfs_cleanup(dev);
 
 err_eq_cleanup:
 	mlx5_eq_cleanup(dev);
@@ -1023,7 +1023,7 @@ static void mlx5_cleanup_once(struct mlx5_core_dev *dev)
 	mlx5_cleanup_mkey_table(dev);
 	mlx5_cleanup_srq_table(dev);
 	mlx5_cleanup_qp_table(dev);
-	mlx5_cleanup_cq_table(dev);
+	mlx5_cq_debugfs_cleanup(dev);
 	mlx5_eq_cleanup(dev);
 }
 

include/linux/mlx5/cq.h

@@ -60,6 +60,7 @@ struct mlx5_core_cq {
 	} tasklet_ctx;
 	int			reset_notify_added;
 	struct list_head	reset_notify;
+	struct mlx5_eq		*eq;
 };
 
 
@@ -171,8 +172,6 @@ static inline void mlx5_cq_arm(struct mlx5_core_cq *cq, u32 cmd,
 	mlx5_write64(doorbell, uar_page + MLX5_CQ_DOORBELL, NULL);
 }
 
-int mlx5_init_cq_table(struct mlx5_core_dev *dev);
-void mlx5_cleanup_cq_table(struct mlx5_core_dev *dev);
 int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
 			u32 *in, int inlen);
 int mlx5_core_destroy_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq);

include/linux/mlx5/driver.h

@@ -375,8 +375,15 @@ struct mlx5_eq_pagefault {
 	mempool_t		*pool;
 };
 
+struct mlx5_cq_table {
+	/* protect radix tree */
+	spinlock_t		lock;
+	struct radix_tree_root	tree;
+};
+
 struct mlx5_eq {
 	struct mlx5_core_dev   *dev;
+	struct mlx5_cq_table	cq_table;
 	__be32 __iomem	       *doorbell;
 	u32			cons_index;
 	struct mlx5_buf		buf;
@@ -526,13 +533,6 @@ struct mlx5_core_health {
 	struct delayed_work		recover_work;
 };
 
-struct mlx5_cq_table {
-	/* protect radix tree
-	 */
-	spinlock_t		lock;
-	struct radix_tree_root	tree;
-};
-
 struct mlx5_qp_table {
 	/* protect radix tree
 	 */
@@ -654,10 +654,6 @@ struct mlx5_priv {
 	struct dentry	       *cmdif_debugfs;
 	/* end: qp staff */
 
-	/* start: cq staff */
-	struct mlx5_cq_table	cq_table;
-	/* end: cq staff */
-
 	/* start: mkey staff */
 	struct mlx5_mkey_table	mkey_table;
 	/* end: mkey staff */
@@ -1053,12 +1049,12 @@ int mlx5_eq_init(struct mlx5_core_dev *dev);
 void mlx5_eq_cleanup(struct mlx5_core_dev *dev);
 void mlx5_fill_page_array(struct mlx5_buf *buf, __be64 *pas);
 void mlx5_fill_page_frag_array(struct mlx5_frag_buf *frag_buf, __be64 *pas);
-void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn);
+void mlx5_cq_completion(struct mlx5_eq *eq, u32 cqn);
 void mlx5_rsc_event(struct mlx5_core_dev *dev, u32 rsn, int event_type);
 void mlx5_srq_event(struct mlx5_core_dev *dev, u32 srqn, int event_type);
 struct mlx5_core_srq *mlx5_core_get_srq(struct mlx5_core_dev *dev, u32 srqn);
 void mlx5_cmd_comp_handler(struct mlx5_core_dev *dev, u64 vec, bool forced);
-void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type);
+void mlx5_cq_event(struct mlx5_eq *eq, u32 cqn, int event_type);
 int mlx5_create_map_eq(struct mlx5_core_dev *dev, struct mlx5_eq *eq, u8 vecidx,
 		       int nent, u64 mask, const char *name,
 		       enum mlx5_eq_type type);