Messages in this thread | | | Date | Wed, 4 Sep 2013 17:44:30 +0530 | From | Vineet Gupta <> | Subject | Query about TX BD Reclaim in Napi poll path (was Re: [PATCH v3] ethernet/arc/arc_emac - Add new driver) |
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Hi Francois,
Resurrecting an old thread.
On 06/14/2013 03:49 AM, Francois Romieu wrote: >> +static irqreturn_t arc_emac_intr(int irq, void *dev_instance) >> > +{ >> > + struct net_device *ndev = dev_instance; >> > + struct arc_emac_priv *priv = netdev_priv(ndev); >> > + struct net_device_stats *stats = &priv->stats; >> > + unsigned int status; >> > + >> > + status = arc_reg_get(priv, R_STATUS); >> > + status &= ~MDIO_MASK; >> > + >> > + /* Reset all flags except "MDIO complete"*/ >> > + arc_reg_set(priv, R_STATUS, status); >> > + >> > + if (status & RXINT_MASK) { >> > + if (likely(napi_schedule_prep(&priv->napi))) { >> > + arc_reg_clr(priv, R_ENABLE, RXINT_MASK); >> > + __napi_schedule(&priv->napi); >> > + } >> > + } >> > + >> > + if (status & TXINT_MASK) { > You may consider moving everything into the napi poll handler.
I has to revisit this now-mainlined driver recently for fixing a bug. Per your suggestion above, the TX BD reclaim was moved from interrupt context to NAPI context. I was wondering if that is the right thing to do (I'm not a networking expert but have worked on this driver heavily before it was mainlined by Alexey).
In case of large burst transfers by networking stack (say a large file copy over NFS) will it not delay the TX BD reclaim possibly dropping more packets. Ofcourse doing this requires enabling Tx interrupts which adds to overall cost from a system perspective, but assuming the controller can coalesce the Tx interrupts, will it not be better.
I did a quick hack to move the TX reclaim in intr path and it seems to be doing slightly better than the current code - so the advantages are not sky high, but I want to understand the implications nevertheless.
TIA, -Vineet
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