Re: [PATCH net-next] mlx4: do not fire tasklet unless necessary

On Fri, Feb 10, 2017 at 2:27 PM, Eric Dumazet [off-list ref] wrote:

From: Eric Dumazet <edumazet@google.com>

All rx and rx netdev interrupts are handled by respectively
by mlx4_en_rx_irq() and mlx4_en_tx_irq() which simply schedule a NAPI.

But mlx4_eq_int() also fires a tasklet to service all items that were
queued via mlx4_add_cq_to_tasklet(), but this handler was not called
unless user cqe was handled.

This is very confusing, as "mpstat -I SCPU ..." show huge number of
tasklet invocations.

This patch saves this overhead, by carefully firing the tasklet directly
from mlx4_add_cq_to_tasklet(), removing four atomic operations per IRQ.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <redacted>
Cc: Saeed Mahameed <redacted>

Acked-by: Saeed Mahameed <redacted>