Re: [PATCH 1/4] igb_uio: add wc option
From: Ferruh Yigit <hidden>
Date: 2018-06-27 16:34:30
On 4/11/2018 3:07 PM, Rafal Kozik wrote:
Write combining (wc) increase NIC performance by making better utilization of PCI bus, but cannot be use by all PMD. Parameter wc_activate add possibility to enable it for those PMD that could support it. Signed-off-by: Rafal Kozik <redacted>
Hi Rafal, First, sorry for delayed comment.
quoted hunk ↗ jump to hunk
--- 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 4cae4dd..42e3b3f 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; + }
Why we need this update at all? What is the relation between internal_address and write combined? As far as I can see we are not using internal_addr at all, what do you observe in write combined usage without this modification?
quoted hunk ↗ jump to hunk
info->mem[n].name = name; info->mem[n].addr = addr; info->mem[n].internal_addr = internal_addr;@@ -638,6 +643,12 @@ 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");