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>
02d92f7903