On Thu, 11 Aug 2016 19:15:40 +0300
Grygorii Strashko <grygorii.strashko@xxxxxx> wrote:
> Mark CPSW Rx/Tx IRQs as IRQF_NO_THREAD and avoid double scheduling on -RT
> where this IRQs are forced threaded:
> rx-irq
> |- schedule threaded rx-irq handler
> ...
> |- threaded rx-irq handler -> cpsw_rx_interrupt()
> |- napi_schedule()
> |- __raise_softirq_irqoff()
> |- wakeup_proper_softirq()
> ...
> napi
>
> after:
> rx-irq
> |- cpsw_rx_interrupt()
> |- napi_schedule()
> |- irq_exit()
> |- invoke_softirq()
> |- wakeup_softirqd()
> ...
> napi
>
> And, as result, get benefits from the following improvements (tested
> on am57xx-evm):
>
> 1) "[ 78.348599] NOHZ: local_softirq_pending 80" message will not be
> seen any more. Now these warnings can be seen once iperf is started.
> # iperf -c $IPERFHOST -w 128K -d -t 60
>
> 2) latency reduction when cyclictest is run in parallel with network load
> where net_perf.sh is:
> iperf -c $IPERFHOST -w 8K -d -t 60
> iperf -c $IPERFHOST -w 16K -d -t 60
> iperf -c $IPERFHOST -w 32K -d -t 60
> iperf -c $IPERFHOST -w 64K -d -t 60
> iperf -c $IPERFHOST -w 128K -d -t 60
>
> before:
> T: 0 ( 1326) P:98 I:1000 C: 240000 Min: 8 Act: 13 Avg: 18 Max: 70
> T: 1 ( 1327) P:98 I:1500 C: 159981 Min: 9 Act: 15 Avg: 16 Max: 43
> after:
> T: 0 ( 1331) P:98 I:1000 C: 240000 Min: 8 Act: 15 Avg: 14 Max: 51
> T: 1 ( 1332) P:98 I:1500 C: 159953 Min: 8 Act: 16 Avg: 15 Max: 33
>
> 3) network performance increase
>
> win, K Mbits/s
> before after %
> 8K 354 350.3 0.0
> 16K 412 551 33.7
> 32K 423 659.5 55.9
> 64K 436 728.3 67.0
> 128K 537 845 57.4
>
> This change does not affect on non-RT.
This looks fine to me, but it should go into the development branch,
which is currently 4.6-rt. And I can then pull it from there.
-- Steve
>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> ---
> Hi All,
>
> I'll be appreciated on any feedback or tested-by.
> In case of positive feedback I'll resend it for upstream.
>
> drivers/net/ethernet/ti/cpsw.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
> index 7b59283..fa4bb81 100644
> --- a/drivers/net/ethernet/ti/cpsw.c
> +++ b/drivers/net/ethernet/ti/cpsw.c
> @@ -769,7 +769,7 @@ static irqreturn_t cpsw_tx_interrupt(int irq, void *dev_id)
> priv->tx_irq_disabled = true;
> }
>
> - napi_schedule(&priv->napi_tx);
> + napi_schedule_irqoff(&priv->napi_tx);
> return IRQ_HANDLED;
> }
>
> @@ -785,7 +785,7 @@ static irqreturn_t cpsw_rx_interrupt(int irq, void *dev_id)
> priv->rx_irq_disabled = true;
> }
>
> - napi_schedule(&priv->napi_rx);
> + napi_schedule_irqoff(&priv->napi_rx);
> return IRQ_HANDLED;
> }
>
> @@ -2827,7 +2827,7 @@ static int cpsw_probe(struct platform_device *pdev)
>
> priv->irqs_table[0] = irq;
> ret = devm_request_irq(&pdev->dev, irq, cpsw_rx_interrupt,
> - 0, dev_name(&pdev->dev), priv);
> + IRQF_NO_THREAD, dev_name(&pdev->dev), priv);
> if (ret < 0) {
> dev_err(priv->dev, "error attaching irq (%d)\n", ret);
> goto clean_ale_ret;
> @@ -2842,7 +2842,7 @@ static int cpsw_probe(struct platform_device *pdev)
>
> priv->irqs_table[1] = irq;
> ret = devm_request_irq(&pdev->dev, irq, cpsw_tx_interrupt,
> - 0, dev_name(&pdev->dev), priv);
> + IRQF_NO_THREAD, dev_name(&pdev->dev), priv);
> if (ret < 0) {
> dev_err(priv->dev, "error attaching irq (%d)\n", ret);
> goto clean_ale_ret;
--
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