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

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Message-ID: <CALzJLG9bFC1nVC1Sp3WiAf_OkO_6O9XYqJGRn21yg32NYey6Vw@mail.gmail.com>
Date:   Thu, 16 Feb 2017 14:38:58 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [PATCH net-next] mlx4: do not fire tasklet unless necessary

On Fri, Feb 10, 2017 at 2:27 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.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@...gle.com>
> Cc: Tariq Toukan <tariqt@...lanox.com>
> Cc: Saeed Mahameed <saeedm@...lanox.com>

Acked-by: Saeed Mahameed <saeedm@...lanox.com>