2018-06-28 16:50 GMT+02:00 Ferruh Yigit <ferruh.yi...@intel.com>: > On 6/28/2018 2:15 PM, Rafal Kozik wrote: >> Write combining (WC) increases NIC performance by making better >> utilization of PCI bus, but cannot be used by all PMDs. >> >> It will be enabled only if RTE_PCI_DRV_WC_ACTIVATE will be set in >> drivers flags. For proper work also igb_uio 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> >> Acked-by: Bruce Richardson <bruce.richard...@intel.com> >> --- >> drivers/bus/pci/linux/pci_uio.c | 41 >> +++++++++++++++++++++++++++++------------ >> drivers/bus/pci/rte_bus_pci.h | 2 ++ >> 2 files changed, 31 insertions(+), 12 deletions(-) >> >> diff --git a/drivers/bus/pci/linux/pci_uio.c >> b/drivers/bus/pci/linux/pci_uio.c >> index d423e4b..e3947c2 100644 >> --- a/drivers/bus/pci/linux/pci_uio.c >> +++ b/drivers/bus/pci/linux/pci_uio.c >> @@ -282,22 +282,19 @@ int >> pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx, >> struct mapped_pci_resource *uio_res, int map_idx) >> { >> - int fd; >> + int fd = -1; >> char devname[PATH_MAX]; >> 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); > > What do you think adding an error log here? If opening resource$_wc fails and > fallback to resource# file, there won't be any way for user to know about it. >
This error will be misleading for two reasons: * even if open return success, it could silently fall-back to non prefetchable mode, * NICs could have multiple BARs, but not all support WC. I such case fails will be desirable. >> + } >> + >> + 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 458e6d0..828acc5 100644 >> --- a/drivers/bus/pci/rte_bus_pci.h >> +++ b/drivers/bus/pci/rte_bus_pci.h >> @@ -135,6 +135,8 @@ 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 */ >> >