On Wed, 2019-02-06 at 09:17 -0800, Eric Dumazet wrote: > > On 02/06/2019 08:55 AM, Saeed Mahameed wrote: > > On Wed, 2019-02-06 at 12:02 +0000, Tariq Toukan wrote: > > > On 2/6/2019 2:35 AM, Cong Wang wrote: > > > > mlx5_eq_cq_get() is called in IRQ handler, the spinlock inside > > > > gets a lot of contentions when we test some heavy workload > > > > with 60 RX queues and 80 CPU's, and it is clearly shown in the > > > > flame graph. > > > > > > > > Hi Cong, > > > > The patch is ok to me, but i really doubt that you can hit a > > contention > > on latest upstream driver, since we already have spinlock per EQ, > > which > > means spinlock per core, each EQ (core) msix handler can only > > access > > one spinlock (its own), so I am surprised how you got the > > contention, > > Maybe you are not running on latest upstream driver ? > > > > what is the workload ? > > Surprisingly (or not), atomic operations, even on _not_ contended > cache lines can > stall the cpu enough for perf tools to notice... > > If the atomic operation can be trivially replaced by RCU, then do it > by any mean. > >
Totally agree, Thanks Eric.
