Thanks John, I'm incorporating your changes into my source tree. I also
plan on changing the
"glue" between mq_start and mq_start_locked on igb after some UDP testing
that was done, and
believe ixgbe should follow suit. Results there have shown the latency is
just too high if I only use
the task_enqueue... What works best is to always queue to the buf ring, but
then also always to
do the TRY_LOCK. I will update HEAD as soon as I handle an internal
firedrill I have today :)
Jack
On Fri, Apr 19, 2013 at 9:27 AM, John Baldwin <j...@freebsd.org> wrote:
> A second patch. This is not something I mentioned before, but I had this
> in
> my checkout. In the legacy IRQ case this could also result in out-of-order
> processing. It also fixes a potential OACTIVE-stuck type bug that we used
> to
> have in igb. I have no way to test this, so it would be good if some other
> folks could test this.
>
> The patch changes ixgbe_txeof() return void and changes the few places that
> checked its return value to ignore it. While it is true that ixgbe has a
> tx
> processing limit (which I think is dubious.. TX completion processing is
> very
> cheap unlike RX processing, so it seems to me like it should always run to
> completion as in igb), in the common case I think the result will be to do
> what igb used to do: poll the ring at 100% CPU (either in the interrupt
> handler or in the task it keeps rescheduling) waiting for pending TX
> packets
> to be completed (which is pointless: the host CPU can't make the NIC
> transmit
> packets any faster by polling).
>
> It also changes the interrupt handlers to restart packet transmission
> synchronously rather than always deferring that to a task (the former is
> what
> (nearly) all other drivers do). It also fixes the interrupt handlers to be
> consistent (one looped on txeof but not the others). In the case of the
> legacy interrupt handler it is possible it could fail to restart packet
> transmission if there were no pending RX packets after rxeof returned and
> txeof fully cleaned its ring without this change.
>
> It also fixes the legacy interrupt handler to not re-enable the interrupt
> if
> it schedules the task but to wait until the task completes (this could
> result
> in concurrent, out-of-order RX processing).
>
> Index: /home/jhb/work/freebsd/svn/head/sys/dev/ixgbe/ixgbe.c
> ===================================================================
> --- /home/jhb/work/freebsd/svn/head/sys/dev/ixgbe/ixgbe.c (revision
> 249553)
> +++ /home/jhb/work/freebsd/svn/head/sys/dev/ixgbe/ixgbe.c (working
> copy)
> @@ -149,7 +149,7 @@
> static void ixgbe_enable_intr(struct adapter *);
> static void ixgbe_disable_intr(struct adapter *);
> static void ixgbe_update_stats_counters(struct adapter *);
> -static bool ixgbe_txeof(struct tx_ring *);
> +static void ixgbe_txeof(struct tx_ring *);
> static bool ixgbe_rxeof(struct ix_queue *);
> static void ixgbe_rx_checksum(u32, struct mbuf *, u32);
> static void ixgbe_set_promisc(struct adapter *);
> @@ -1431,7 +1414,10 @@
> }
>
> /* Reenable this interrupt */
> - ixgbe_enable_queue(adapter, que->msix);
> + if (que->res != NULL)
> + ixgbe_enable_queue(adapter, que->msix);
> + else
> + ixgbe_enable_intr(adapter);
> return;
> }
>
> @@ -1449,8 +1435,9 @@
> struct adapter *adapter = que->adapter;
> struct ixgbe_hw *hw = &adapter->hw;
> struct tx_ring *txr = adapter->tx_rings;
> - bool more_tx, more_rx;
> - u32 reg_eicr, loop = MAX_LOOP;
> + struct ifnet *ifp = adapter->ifp;
> + bool more;
> + u32 reg_eicr;
>
>
> reg_eicr = IXGBE_READ_REG(hw, IXGBE_EICR);
> @@ -1461,17 +1448,19 @@
> return;
> }
>
> - more_rx = ixgbe_rxeof(que);
> + more = ixgbe_rxeof(que);
>
> IXGBE_TX_LOCK(txr);
> - do {
> - more_tx = ixgbe_txeof(txr);
> - } while (loop-- && more_tx);
> + ixgbe_txeof(txr);
> +#if __FreeBSD_version >= 800000
> + if (!drbr_empty(ifp, txr->br))
> + ixgbe_mq_start_locked(ifp, txr, NULL);
> +#else
> + if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
> + ixgbe_start_locked(txr, ifp);
> +#endif
> IXGBE_TX_UNLOCK(txr);
>
> - if (more_rx || more_tx)
> - taskqueue_enqueue(que->tq, &que->que_task);
> -
> /* Check for fan failure */
> if ((hw->phy.media_type == ixgbe_media_type_copper) &&
> (reg_eicr & IXGBE_EICR_GPI_SDP1)) {
> @@ -1484,7 +1473,10 @@
> if (reg_eicr & IXGBE_EICR_LSC)
> taskqueue_enqueue(adapter->tq, &adapter->link_task);
>
> - ixgbe_enable_intr(adapter);
> + if (more)
> + taskqueue_enqueue(que->tq, &que->que_task);
> + else
> + ixgbe_enable_intr(adapter);
> return;
> }
>
> @@ -1501,27 +1493,24 @@
> struct adapter *adapter = que->adapter;
> struct tx_ring *txr = que->txr;
> struct rx_ring *rxr = que->rxr;
> - bool more_tx, more_rx;
> + struct ifnet *ifp = adapter->ifp;
> + bool more;
> u32 newitr = 0;
>
> ixgbe_disable_queue(adapter, que->msix);
> ++que->irqs;
>
> - more_rx = ixgbe_rxeof(que);
> + more = ixgbe_rxeof(que);
>
> IXGBE_TX_LOCK(txr);
> - more_tx = ixgbe_txeof(txr);
> - /*
> - ** Make certain that if the stack
> - ** has anything queued the task gets
> - ** scheduled to handle it.
> - */
> + ixgbe_txeof(txr);
> #ifdef IXGBE_LEGACY_TX
> if (!IFQ_DRV_IS_EMPTY(&adapter->ifp->if_snd))
> + ixgbe_start_locked(txr, ifp);
> #else
> - if (!drbr_empty(adapter->ifp, txr->br))
> + if (!drbr_empty(ifp, txr->br))
> + ixgbe_mq_start_locked(ifp, txr, NULL);
> #endif
> - more_tx = 1;
> IXGBE_TX_UNLOCK(txr);
>
> /* Do AIM now? */
> @@ -1575,7 +1564,7 @@
> rxr->packets = 0;
>
> no_calc:
> - if (more_tx || more_rx)
> + if (more)
> taskqueue_enqueue(que->tq, &que->que_task);
> else /* Reenable this interrupt */
> ixgbe_enable_queue(adapter, que->msix);
> @@ -3557,7 +3545,7 @@
> * tx_buffer is put back on the free queue.
> *
> **********************************************************************/
> -static bool
> +static void
> ixgbe_txeof(struct tx_ring *txr)
> {
> struct adapter *adapter = txr->adapter;
> @@ -3605,13 +3593,13 @@
> IXGBE_CORE_UNLOCK(adapter);
> IXGBE_TX_LOCK(txr);
> }
> - return FALSE;
> + return;
> }
> #endif /* DEV_NETMAP */
>
> if (txr->tx_avail == txr->num_desc) {
> txr->queue_status = IXGBE_QUEUE_IDLE;
> - return FALSE;
> + return;
> }
>
> /* Get work starting point */
> @@ -3705,12 +3693,8 @@
> if ((!processed) && ((ticks - txr->watchdog_time) >
> IXGBE_WATCHDOG))
> txr->queue_status = IXGBE_QUEUE_HUNG;
>
> - if (txr->tx_avail == txr->num_desc) {
> + if (txr->tx_avail == txr->num_desc)
> txr->queue_status = IXGBE_QUEUE_IDLE;
> - return (FALSE);
> - }
> -
> - return TRUE;
> }
>
> /*********************************************************************
>
>
> --
> John Baldwin
>
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