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Date: Tue, 27 Apr 2010 04:37:20 -0700
From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, gospo@...hat.com,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next-2.6 PATCH 1/2] ixgbe: enable extremely low latency
From: Jesse Brandeburg <jesse.brandeburg@...el.com>
82598/82599 can support EITR == 0, which allows for the
absolutely lowest latency setting in the hardware. This disables
writeback batching and anything else that relies upon a delayed
interrupt. This patch enables the feature of "override" when a
user sets rx-usecs to zero, the driver will respect that setting
over using RSC, and automatically disable RSC. If rx-usecs is
used to set the EITR value to 0, then the driver should disable
LRO (aka RSC) internally until EITR is set to non-zero again.
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
drivers/net/ixgbe/ixgbe_ethtool.c | 87 +++++++++++++++++++++++++++++++++----
drivers/net/ixgbe/ixgbe_main.c | 9 ++++
2 files changed, 87 insertions(+), 9 deletions(-)
diff --git a/drivers/net/ixgbe/ixgbe_ethtool.c b/drivers/net/ixgbe/ixgbe_ethtool.c
index 7b391f9..b72a997 100644
--- a/drivers/net/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ixgbe/ixgbe_ethtool.c
@@ -2079,6 +2079,27 @@ static int ixgbe_get_coalesce(struct net_device *netdev,
return 0;
}
+/*
+ * this function must be called before setting the new value of
+ * rx_itr_setting
+ */
+static void ixgbe_reenable_rsc(struct ixgbe_adapter *adapter,
+ struct ethtool_coalesce *ec)
+{
+ /* check the old value and enable RSC if necessary */
+ if ((adapter->rx_itr_setting == 0) &&
+ (adapter->flags2 & IXGBE_FLAG2_RSC_CAPABLE)) {
+ adapter->flags2 |= IXGBE_FLAG2_RSC_ENABLED;
+ adapter->netdev->features |= NETIF_F_LRO;
+ DPRINTK(PROBE, INFO, "rx-usecs set to %d, re-enabling RSC\n",
+ ec->rx_coalesce_usecs);
+ if (netif_running(adapter->netdev))
+ ixgbe_reinit_locked(adapter);
+ else
+ ixgbe_reset(adapter);
+ }
+}
+
static int ixgbe_set_coalesce(struct net_device *netdev,
struct ethtool_coalesce *ec)
{
@@ -2095,11 +2116,20 @@ static int ixgbe_set_coalesce(struct net_device *netdev,
adapter->tx_ring[0]->work_limit = ec->tx_max_coalesced_frames_irq;
if (ec->rx_coalesce_usecs > 1) {
+ u32 max_int;
+ if (adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED)
+ max_int = IXGBE_MAX_RSC_INT_RATE;
+ else
+ max_int = IXGBE_MAX_INT_RATE;
+
/* check the limits */
- if ((1000000/ec->rx_coalesce_usecs > IXGBE_MAX_INT_RATE) ||
+ if ((1000000/ec->rx_coalesce_usecs > max_int) ||
(1000000/ec->rx_coalesce_usecs < IXGBE_MIN_INT_RATE))
return -EINVAL;
+ /* check the old value and enable RSC if necessary */
+ ixgbe_reenable_rsc(adapter, ec);
+
/* store the value in ints/second */
adapter->rx_eitr_param = 1000000/ec->rx_coalesce_usecs;
@@ -2108,6 +2138,9 @@ static int ixgbe_set_coalesce(struct net_device *netdev,
/* clear the lower bit as its used for dynamic state */
adapter->rx_itr_setting &= ~1;
} else if (ec->rx_coalesce_usecs == 1) {
+ /* check the old value and enable RSC if necessary */
+ ixgbe_reenable_rsc(adapter, ec);
+
/* 1 means dynamic mode */
adapter->rx_eitr_param = 20000;
adapter->rx_itr_setting = 1;
@@ -2116,14 +2149,34 @@ static int ixgbe_set_coalesce(struct net_device *netdev,
* any other value means disable eitr, which is best
* served by setting the interrupt rate very high
*/
- if (adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED)
- adapter->rx_eitr_param = IXGBE_MAX_RSC_INT_RATE;
- else
- adapter->rx_eitr_param = IXGBE_MAX_INT_RATE;
+ adapter->rx_eitr_param = IXGBE_MAX_INT_RATE;
adapter->rx_itr_setting = 0;
+
+ /*
+ * if hardware RSC is enabled, disable it when
+ * setting low latency mode, to avoid errata, assuming
+ * that when the user set low latency mode they want
+ * it at the cost of anything else
+ */
+ if (adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED) {
+ adapter->flags2 &= ~IXGBE_FLAG2_RSC_ENABLED;
+ netdev->features &= ~NETIF_F_LRO;
+ DPRINTK(PROBE, INFO,
+ "rx-usecs set to 0, disabling RSC\n");
+
+ if (netif_running(netdev))
+ ixgbe_reinit_locked(adapter);
+ else
+ ixgbe_reset(adapter);
+ return 0;
+ }
}
if (ec->tx_coalesce_usecs > 1) {
+ /*
+ * don't have to worry about max_int as above because
+ * tx vectors don't do hardware RSC (an rx function)
+ */
/* check the limits */
if ((1000000/ec->tx_coalesce_usecs > IXGBE_MAX_INT_RATE) ||
(1000000/ec->tx_coalesce_usecs < IXGBE_MIN_INT_RATE))
@@ -2178,10 +2231,26 @@ static int ixgbe_set_flags(struct net_device *netdev, u32 data)
ethtool_op_set_flags(netdev, data);
/* if state changes we need to update adapter->flags and reset */
- if ((!!(data & ETH_FLAG_LRO)) !=
- (!!(adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED))) {
- adapter->flags2 ^= IXGBE_FLAG2_RSC_ENABLED;
- need_reset = true;
+ if (adapter->flags2 & IXGBE_FLAG2_RSC_CAPABLE) {
+ /*
+ * cast both to bool and verify if they are set the same
+ * but only enable RSC if itr is non-zero, as
+ * itr=0 and RSC are mutually exclusive
+ */
+ if (((!!(data & ETH_FLAG_LRO)) !=
+ (!!(adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED))) &&
+ adapter->rx_itr_setting) {
+ adapter->flags2 ^= IXGBE_FLAG2_RSC_ENABLED;
+ switch (adapter->hw.mac.type) {
+ case ixgbe_mac_82599EB:
+ need_reset = true;
+ break;
+ default:
+ break;
+ }
+ } else if (!adapter->rx_itr_setting) {
+ netdev->features &= ~ETH_FLAG_LRO;
+ }
}
/*
diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
index 32781b3..0c4ca68 100644
--- a/drivers/net/ixgbe/ixgbe_main.c
+++ b/drivers/net/ixgbe/ixgbe_main.c
@@ -1190,6 +1190,15 @@ void ixgbe_write_eitr(struct ixgbe_q_vector *q_vector)
itr_reg |= (itr_reg << 16);
} else if (adapter->hw.mac.type == ixgbe_mac_82599EB) {
/*
+ * 82599 can support a value of zero, so allow it for
+ * max interrupt rate, but there is an errata where it can
+ * not be zero with RSC
+ */
+ if (itr_reg == 8 &&
+ !(adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED))
+ itr_reg = 0;
+
+ /*
* set the WDIS bit to not clear the timer bits and cause an
* immediate assertion of the interrupt
*/
--
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