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, 1 insertions, 2 deletions

diff --git a/include/linux/mlx5/cq.h b/include/linux/mlx5/cq.h
index 48c181a2acc9..06ba425a6ad7 100644
--- a/include/linux/mlx5/cq.h
+++ b/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);