Write combining (WC) increases NIC performance by making better utilization of PCI bus, but cannot be use by all PMDs.
To get internal_addr memory need to be mapped. But as memory could not be mapped twice: with and without WC, it should be skipped for WC. [1] To do not spoil other drivers that potentially could use internal_addr, parameter wc_activate adds possibility to skip it for those PMDs, that do not use it. [1] https://www.kernel.org/doc/ols/2008/ols2008v2-pages-135-144.pdf section 5.3 and 5.4 Signed-off-by: Rafal Kozik <r...@semihalf.com> Acked-by: Bruce Richardson <bruce.richard...@intel.com> --- kernel/linux/igb_uio/igb_uio.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c index b3233f1..3382fb1 100644 --- a/kernel/linux/igb_uio/igb_uio.c +++ b/kernel/linux/igb_uio/igb_uio.c @@ -30,6 +30,7 @@ struct rte_uio_pci_dev { int refcnt; }; +static int wc_activate; static char *intr_mode; static enum rte_intr_mode igbuio_intr_mode_preferred = RTE_INTR_MODE_MSIX; /* sriov sysfs */ @@ -375,9 +376,13 @@ igbuio_pci_setup_iomem(struct pci_dev *dev, struct uio_info *info, len = pci_resource_len(dev, pci_bar); if (addr == 0 || len == 0) return -1; - internal_addr = ioremap(addr, len); - if (internal_addr == NULL) - return -1; + if (wc_activate == 0) { + internal_addr = ioremap(addr, len); + if (internal_addr == NULL) + return -1; + } else { + internal_addr = NULL; + } info->mem[n].name = name; info->mem[n].addr = addr; info->mem[n].internal_addr = internal_addr; @@ -650,6 +655,12 @@ MODULE_PARM_DESC(intr_mode, " " RTE_INTR_MODE_LEGACY_NAME " Use Legacy interrupt\n" "\n"); +module_param(wc_activate, int, 0); +MODULE_PARM_DESC(wc_activate, +"Activate support for write combining (WC) (default=0)\n" +" 0 - disable\n" +" other - enable\n"); + MODULE_DESCRIPTION("UIO driver for Intel IGB PCI cards"); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Intel Corporation"); -- 2.7.4
