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>

1 files changed, 9 insertions, 13 deletions

diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index 6ed79a8a8318..96e003db2bcd 100644
--- a/include/linux/mlx5/driver.h
+++ b/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);