Re: [PATCH net-next v2 06/10] net: stmmac: Do not disable interrupts when cleaning TX
On Mon, Jul 1, 2019 at 6:15 AM Jose Abreu wrote:
>
> From: Willem de Bruijn
>
> > By the
> >
> > if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
> > stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
> > napi_schedule_irqoff(>rx_napi);
> > }
> >
> > branch directly above? If so, is it possible to have fewer rx than tx
> > queues and miss this?
>
> Yes, it is possible.
And that is not a problem?
>
> > this logic seems more complex than needed?
> >
> > if (status)
> > status |= handle_rx | handle_tx;
> >
> > if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
> >
> > }
> >
> > if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
> >
> > }
> >
> > status & handle_rx implies status & handle_tx and vice versa.
>
> This is removed in patch 09/10.
>
> > > - if (work_done < budget && napi_complete_done(napi, work_done))
> > > - stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
> > > + if (work_done < budget)
> > > + napi_complete_done(napi, work_done);
> >
> > It does seem odd that stmmac_napi_poll_rx and stmmac_napi_poll_tx both
> > call stmmac_enable_dma_irq(..) independent of the other. Shouldn't the
> > IRQ remain masked while either is active or scheduled? That is almost
> > what this patch does, though not exactly.
>
> After patch 09/10 the interrupts will only be disabled by RX NAPI and
> re-enabled by it again. I can do some tests on whether disabling
> interrupts independently gives more performance but I wouldn't expect so
> because the real bottleneck when I do iperf3 tests is the RX path ...
Sharing the IRQ sounds fine. My only concern was TX-only IRQs in case
more TX than RX queues are configured. If that is possible with this
driver.
RE: [PATCH net-next v2 06/10] net: stmmac: Do not disable interrupts when cleaning TX
From: Willem de Bruijn
> By the
>
> if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
> stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
> napi_schedule_irqoff(>rx_napi);
> }
>
> branch directly above? If so, is it possible to have fewer rx than tx
> queues and miss this?
Yes, it is possible.
> this logic seems more complex than needed?
>
> if (status)
> status |= handle_rx | handle_tx;
>
> if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
>
> }
>
> if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
>
> }
>
> status & handle_rx implies status & handle_tx and vice versa.
This is removed in patch 09/10.
> > - if (work_done < budget && napi_complete_done(napi, work_done))
> > - stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
> > + if (work_done < budget)
> > + napi_complete_done(napi, work_done);
>
> It does seem odd that stmmac_napi_poll_rx and stmmac_napi_poll_tx both
> call stmmac_enable_dma_irq(..) independent of the other. Shouldn't the
> IRQ remain masked while either is active or scheduled? That is almost
> what this patch does, though not exactly.
After patch 09/10 the interrupts will only be disabled by RX NAPI and
re-enabled by it again. I can do some tests on whether disabling
interrupts independently gives more performance but I wouldn't expect so
because the real bottleneck when I do iperf3 tests is the RX path ...
Re: [PATCH net-next v2 06/10] net: stmmac: Do not disable interrupts when cleaning TX
On Fri, Jun 28, 2019 at 3:30 AM Jose Abreu wrote:
>
> This is a performance killer and anyways the interrupts are being
> disabled by RX NAPI so no need to disable them again.
By the
if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
napi_schedule_irqoff(>rx_napi);
}
branch directly above? If so, is it possible to have fewer rx than tx
queues and miss this?
this logic seems more complex than needed?
if (status)
status |= handle_rx | handle_tx;
if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
}
if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
}
status & handle_rx implies status & handle_tx and vice versa.
>
> Signed-off-by: Jose Abreu
> Cc: Joao Pinto
> Cc: David S. Miller
> Cc: Giuseppe Cavallaro
> Cc: Alexandre Torgue
> ---
> drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8 +++-
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 4a5941caaadc..e8f3e76889c8 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2061,10 +2061,8 @@ static int stmmac_napi_check(struct stmmac_priv *priv,
> u32 chan)
> napi_schedule_irqoff(>rx_napi);
> }
>
> - if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
> - stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
> + if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use))
> napi_schedule_irqoff(>tx_napi);
> - }
>
> return status;
> }
> @@ -3570,8 +3568,8 @@ static int stmmac_napi_poll_tx(struct napi_struct
> *napi, int budget)
> work_done = stmmac_tx_clean(priv, DMA_TX_SIZE, chan);
> work_done = min(work_done, budget);
>
> - if (work_done < budget && napi_complete_done(napi, work_done))
> - stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
> + if (work_done < budget)
> + napi_complete_done(napi, work_done);
It does seem odd that stmmac_napi_poll_rx and stmmac_napi_poll_tx both
call stmmac_enable_dma_irq(..) independent of the other. Shouldn't the
IRQ remain masked while either is active or scheduled? That is almost
what this patch does, though not exactly.
