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igb: reduce CPU0 latency when updating statistics 

This change is based off of the work and suggestion of Jan Jablonsky
<jan.jablonsky@thalesgroup.com>.

The Watchdog workqueue in igb driver is scheduled every 2s for each
network interface. That includes updating a statistics protected by
spinlock. Function igb_update_stats in this case will be protected
against preemption. According to number of a statistics registers
(cca 60), processing this function might cause additional cpu load
 on CPU0.

In case of statistics spinlock may be replaced with mutex, which
reduce latency on CPU0.

CC: Bernhard Kaindl  <bernhard.kaindl@thalesgroup.com>
CC: Jan Jablonsky <jan.jablonsky@thalesgroup.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Jeff Kirsher 2018-08-02 10:13:10 -07:00
parent 44a7b3b6e3
commit 59361316af
3 changed files with 10 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/ethernet/intel/igb/igb.h
View File

@ -515,7 +515,7 @@ struct igb_adapter {
/* OS defined structs */
struct pci_dev *pdev;
spinlock_t stats64_lock;
struct mutex stats64_lock;
struct rtnl_link_stats64 stats64;
/* structs defined in e1000_hw.h */

4
drivers/net/ethernet/intel/igb/igb_ethtool.c
View File

@ -2295,7 +2295,7 @@ static void igb_get_ethtool_stats(struct net_device *netdev,
int i, j;
char *p;
spin_lock(&adapter->stats64_lock);
mutex_lock(&adapter->stats64_lock);
igb_update_stats(adapter);
for (i = 0; i < IGB_GLOBAL_STATS_LEN; i++) {
@ -2338,7 +2338,7 @@ static void igb_get_ethtool_stats(struct net_device *netdev,
} while (u64_stats_fetch_retry_irq(&ring->rx_syncp, start));
i += IGB_RX_QUEUE_STATS_LEN;
}
spin_unlock(&adapter->stats64_lock);
mutex_unlock(&adapter->stats64_lock);
}
static void igb_get_strings(struct net_device *netdev, u32 stringset, u8 *data)

14
drivers/net/ethernet/intel/igb/igb_main.c
View File

@ -2203,9 +2203,9 @@ void igb_down(struct igb_adapter *adapter)
del_timer_sync(&adapter->phy_info_timer);
/* record the stats before reset*/
spin_lock(&adapter->stats64_lock);
mutex_lock(&adapter->stats64_lock);
igb_update_stats(adapter);
spin_unlock(&adapter->stats64_lock);
mutex_unlock(&adapter->stats64_lock);
adapter->link_speed = 0;
adapter->link_duplex = 0;
@ -3840,7 +3840,7 @@ static int igb_sw_init(struct igb_adapter *adapter)
adapter->min_frame_size = ETH_ZLEN + ETH_FCS_LEN;
spin_lock_init(&adapter->nfc_lock);
spin_lock_init(&adapter->stats64_lock);
mutex_init(&adapter->stats64_lock);
#ifdef CONFIG_PCI_IOV
switch (hw->mac.type) {
case e1000_82576:
@ -5406,9 +5406,9 @@ static void igb_watchdog_task(struct work_struct *work)
}
}
spin_lock(&adapter->stats64_lock);
mutex_lock(&adapter->stats64_lock);
igb_update_stats(adapter);
spin_unlock(&adapter->stats64_lock);
mutex_unlock(&adapter->stats64_lock);
for (i = 0; i < adapter->num_tx_queues; i++) {
struct igb_ring *tx_ring = adapter->tx_ring[i];
@ -6235,10 +6235,10 @@ static void igb_get_stats64(struct net_device *netdev,
{
struct igb_adapter *adapter = netdev_priv(netdev);
spin_lock(&adapter->stats64_lock);
mutex_lock(&adapter->stats64_lock);
igb_update_stats(adapter);
memcpy(stats, &adapter->stats64, sizeof(*stats));
spin_unlock(&adapter->stats64_lock);
mutex_unlock(&adapter->stats64_lock);
}
/**