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Commit 28b581ab authored by Neil Turton's avatar Neil Turton Committed by David S. Miller
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sfc: Add option to use a separate channel for TX completions 



In a bidirectional forwarding test, we find that the best performance
is achieved by sending the TX completion interrupts from one NIC to a
CPU which shares an L2 cache with RX completion interrupts from the
other NIC.  To facilitate this, add an option (through a module
parameter) to create separate channels for RX and TX completion with
separate IRQs when MSI-X is available.

Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 84ae48fe

drivers/net/sfc/efx.c

+26 −15
Original line number Diff line number Diff line
@@ -64,13 +64,15 @@ MODULE_PARM_DESC(lro, "Large receive offload acceleration"); 
/*

 * Use separate channels for TX and RX events

 *

 * Set this to 1 to use separate channels for TX and RX. It allows us to

 * apply a higher level of interrupt moderation to TX events.

 * Set this to 1 to use separate channels for TX and RX. It allows us

 * to control interrupt affinity separately for TX and RX.

 *

 * This is forced to 0 for MSI interrupt mode as the interrupt vector

 * is not written

 * This is only used in MSI-X interrupt mode

 */

static unsigned int separate_tx_and_rx_channels = true;

static unsigned int separate_tx_channels;

module_param(separate_tx_channels, uint, 0644);

MODULE_PARM_DESC(separate_tx_channels,

		 "Use separate channels for TX and RX");



/* This is the weight assigned to each of the (per-channel) virtual

 * NAPI devices.
@@ -846,26 +848,33 @@ static void efx_probe_interrupts(struct efx_nic *efx) 
	if (efx->interrupt_mode == EFX_INT_MODE_MSIX) {

		struct msix_entry xentries[EFX_MAX_CHANNELS];

		int wanted_ints;

		int rx_queues;



		/* We want one RX queue and interrupt per CPU package

		 * (or as specified by the rss_cpus module parameter).

		 * We will need one channel per interrupt.

		 */

		wanted_ints = rss_cpus ? rss_cpus : efx_wanted_rx_queues();

		efx->n_rx_queues = min(wanted_ints, max_channels);

		rx_queues = rss_cpus ? rss_cpus : efx_wanted_rx_queues();

		wanted_ints = rx_queues + (separate_tx_channels ? 1 : 0);

		wanted_ints = min(wanted_ints, max_channels);



		for (i = 0; i < efx->n_rx_queues; i++)

		for (i = 0; i < wanted_ints; i++)

			xentries[i].entry = i;

		rc = pci_enable_msix(efx->pci_dev, xentries, efx->n_rx_queues);

		rc = pci_enable_msix(efx->pci_dev, xentries, wanted_ints);

		if (rc > 0) {

			EFX_BUG_ON_PARANOID(rc >= efx->n_rx_queues);

			efx->n_rx_queues = rc;

			EFX_ERR(efx, "WARNING: Insufficient MSI-X vectors"

				" available (%d < %d).\n", rc, wanted_ints);

			EFX_ERR(efx, "WARNING: Performance may be reduced.\n");

			EFX_BUG_ON_PARANOID(rc >= wanted_ints);

			wanted_ints = rc;

			rc = pci_enable_msix(efx->pci_dev, xentries,

					     efx->n_rx_queues);

					     wanted_ints);

		}



		if (rc == 0) {

			for (i = 0; i < efx->n_rx_queues; i++)

			efx->n_rx_queues = min(rx_queues, wanted_ints);

			efx->n_channels = wanted_ints;

			for (i = 0; i < wanted_ints; i++)

				efx->channel[i].irq = xentries[i].vector;

		} else {

			/* Fall back to single channel MSI */
@@ -877,6 +886,7 @@ static void efx_probe_interrupts(struct efx_nic *efx) 
	/* Try single interrupt MSI */

	if (efx->interrupt_mode == EFX_INT_MODE_MSI) {

		efx->n_rx_queues = 1;

		efx->n_channels = 1;

		rc = pci_enable_msi(efx->pci_dev);

		if (rc == 0) {

			efx->channel[0].irq = efx->pci_dev->irq;
@@ -889,6 +899,7 @@ static void efx_probe_interrupts(struct efx_nic *efx) 
	/* Assume legacy interrupts */

	if (efx->interrupt_mode == EFX_INT_MODE_LEGACY) {

		efx->n_rx_queues = 1;

		efx->n_channels = 1 + (separate_tx_channels ? 1 : 0);

		efx->legacy_irq = efx->pci_dev->irq;

	}

}
@@ -913,8 +924,8 @@ static void efx_set_channels(struct efx_nic *efx) 
	struct efx_rx_queue *rx_queue;



	efx_for_each_tx_queue(tx_queue, efx) {

		if (!EFX_INT_MODE_USE_MSI(efx) && separate_tx_and_rx_channels)

			tx_queue->channel = &efx->channel[1];

		if (separate_tx_channels)

			tx_queue->channel = &efx->channel[efx->n_channels-1];

		else

			tx_queue->channel = &efx->channel[0];

		tx_queue->channel->used_flags |= EFX_USED_BY_TX;

drivers/net/sfc/net_driver.h

+2 −0
Original line number Diff line number Diff line
@@ -649,6 +649,7 @@ union efx_multicast_hash { 
 * @rx_queue: RX DMA queues

 * @channel: Channels

 * @n_rx_queues: Number of RX queues

 * @n_channels: Number of channels in use

 * @rx_buffer_len: RX buffer length

 * @rx_buffer_order: Order (log2) of number of pages for each RX buffer

 * @irq_status: Interrupt status buffer
@@ -728,6 +729,7 @@ struct efx_nic { 
	struct efx_channel channel[EFX_MAX_CHANNELS];



	int n_rx_queues;

	int n_channels;

	unsigned int rx_buffer_len;

	unsigned int rx_buffer_order;