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 <r...@semihalf.com> --- 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) { + 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 */ -- 2.7.4