2018-06-27 18:41 GMT+02:00 Ferruh Yigit [off-list ref]:

On 4/11/2018 3:07 PM, Rafal Kozik wrote:

quoted

Write combining (wc) increase NIC performenca by making better
utilization of PCI bus, but cannot be used by all PMD.

It will be enable only if RTE_PCI_DRV_WC_ACTIVATE will be set in
drivers flags. For proper work also igb driver must be loaded with
wc_activate set to 1.

When mapping PCI resources firstly try to us wc.
If it is not supported it will fallback to normal mode.

Signed-off-by: Rafal Kozik <redacted>
---
 drivers/bus/pci/linux/pci_uio.c | 39 ++++++++++++++++++++++++++++-----------
 drivers/bus/pci/rte_bus_pci.h   |  2 ++
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
index d423e4b..a1570c9 100644
--- a/drivers/bus/pci/linux/pci_uio.c
+++ b/drivers/bus/pci/linux/pci_uio.c

@@ -287,17 +287,14 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
      void *mapaddr;
      struct rte_pci_addr *loc;
      struct pci_map *maps;
+     int wc_activate = 0;
+
+     if (dev->driver != NULL)
+             wc_activate = dev->driver->drv_flags & RTE_PCI_DRV_WC_ACTIVATE;

      loc = &dev->addr;
      maps = uio_res->maps;

-     /* update devname for mmap  */
-     snprintf(devname, sizeof(devname),
-                     "%s/" PCI_PRI_FMT "/resource%d",
-                     rte_pci_get_sysfs_path(),
-                     loc->domain, loc->bus, loc->devid,
-                     loc->function, res_idx);
-
      /* allocate memory to keep path */
      maps[map_idx].path = rte_malloc(NULL, strlen(devname) + 1, 0);
      if (maps[map_idx].path == NULL) {

@@ -309,11 +306,31 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
      /*
       * open resource file, to mmap it
       */
-     fd = open(devname, O_RDWR);
-     if (fd < 0) {
-             RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
+     if (wc_activate) {
+             /* update devname for mmap  */
+             snprintf(devname, sizeof(devname),
+                     "%s/" PCI_PRI_FMT "/resource%d_wc",
+                     rte_pci_get_sysfs_path(),
+                     loc->domain, loc->bus, loc->devid,
+                     loc->function, res_idx);
+
+             fd = open(devname, O_RDWR);
+     }
+
+     if (!wc_activate || fd < 0) {

"fd" may be used uninitialized here, although its value doesn't affect the
branch taken it can be good to initialize it for any possible static analyzer
warning.

I will fix it in new, rebased patch set.

quoted

+             snprintf(devname, sizeof(devname),
+                     "%s/" PCI_PRI_FMT "/resource%d",
+                     rte_pci_get_sysfs_path(),
+                     loc->domain, loc->bus, loc->devid,
+                     loc->function, res_idx);
+
+             /* then try to map resource file */
+             fd = open(devname, O_RDWR);
+             if (fd < 0) {
+                     RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
                              devname, strerror(errno));
-             goto error;
+                     goto error;
+             }
      }

      /* try mapping somewhere close to the end of hugepages */

diff --git a/drivers/bus/pci/rte_bus_pci.h b/drivers/bus/pci/rte_bus_pci.h
index 357afb9..b7bcce3 100644
--- a/drivers/bus/pci/rte_bus_pci.h
+++ b/drivers/bus/pci/rte_bus_pci.h

@@ -132,6 +132,8 @@ struct rte_pci_bus {

 /** Device needs PCI BAR mapping (done with either IGB_UIO or VFIO) */
 #define RTE_PCI_DRV_NEED_MAPPING 0x0001
+/** Device needs PCI BAR mapping with enabled write combining (wc) */
+#define RTE_PCI_DRV_WC_ACTIVATE 0x0002
 /** Device driver supports link state interrupt */
 #define RTE_PCI_DRV_INTR_LSC 0x0008
 /** Device driver supports device removal interrupt */