On 4/11/2018 3:07 PM, Rafal Kozik wrote:
> 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) {
"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.
> + 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 */
>
